If you have sex with a woman on a second date does that prevent you from taking her seriously as a potential girlfriend, or would you not have gone out with her a second time if you didn’t think that potential was there?
It would be a positive sign for me, generally. I might be a little careful to be sure that I wasn’t just letting my hormones get the better of me, but it wouldn’t make me take her less seriously as a potential long-term partner.
Same here. I’d actually admire her restraint, considering what a stud-muffin I am! 
An analogy much used in my younger days:
A woman is like a castle, a man attempts to attack the castle, the walls may be too high the battlements may be impenetrable, but if you succeed, if you scale the central keep and you intend to hold on to the castle you then look from the watchtower at the hordes amassing on the horizon and assess your defenses. You ask yourself how hard would it be for someone else to get in.
Now my opinion is:
Every womans different, just stay away from a serious relationship with any woman 19 to 24.
Fior me, sex prior to the first date wasn’t necessarily a deal breaker.
I don’t sleep with women…but I never thought less of the guys I slept with. My long term relationships have both started with sex very early on.
<pulls up drawbridge, stocks moat with crocodiles, katie-bars door, and positions archers with flaming tar…>
RE the OP–
Who knows? Everybody is different, men and women. Some men would and some would not. Some women would etc. I’d say that if this has already occurred and he said he’d call you and it’s been 4 days and no call–I wouldn’t wait around for him to call (unless he had to leave on a top secret diplomatic mission or visit his mother). I don’t know that there is a general consensus. Sorry.
I’ll endorse the second half of your “or” statement, having a second date implied I already saw potential.
I do hope that sex on the second date doesn’t preclude a long-term relationship. I just married her…
As I’ve explained in other threads, even sex on the first date doesn’t predict relationship failure to me. It should, however, indicate that more dates are in your future, ie: don’t sleep with her unless you are hopeful about a more dates.
Sitnam’s example is a bad one, IMO. It implies that the woman’s job is to keep the man out and if it was easy for him, then it might be easy for others. If the man’s morals don’t allow the woman to permit an easy breach of her walls, then he shouldn’t be scaling them, either. …and I think I’ve just strained my analogy muscles…
Depends on the sex. Sex without chemistry = not taking her seriously unless some significant discoveries happen further down the road.
If we just turbo’d through the chemistry and everything was perfect despite both our best efforts to find fault then I would already consider her a long term GF even if it was 2 hours into the first date.
There’s no rule that says you can’t act on instinct and end up being right later on.
This has already happened but it isn’t that he isn’t calling me or anything. I talked to him yesterday and he is staying at my place on Friday night so we are seeing one another again. I really, really like him (hence the sex on Monday) and I just don’t want to have screwed this up by sleeping with him too soon. He snuggled with me for at least an hour afterward and walked me to the subway so I think that was a good sign. 
I just haven’t had sex with a man in a really long time up until Monday and I am overthinking it a bit I suppose.
A second date is like a second interview, it implies the interest is there. Sitnam just gave me a headache.
Here’s my opinion - go with your gut - not some timeline.
My first date with Dewey D lasted 23 hours - and somewhere around like hour 13 we were doing the horizontal mambo (with additional dances occuring for the next 10 hours). Fastfoward and we just celebrated our 4-monthiversary yesterday with no end in site.
Typically, I have found that my more serious relationships did not start out with sex right away (aka 1st or 2nd date).
But I can honestly say - this is my best relationship ever and we were turbo-charged.
So go with what you see - not the timelines that Emily Post et al set.
I may be labeled an asshole for this but if I don’t get it by the third date then I’m probably going to break it off. Simply because we obviously don’t hold the same views about sex.
I realize that logic may be flawed but there you have it.
I’d even consider a girl as a potential GF if she gave it up on the FIRST date.
But that’s only under the condition it was an actual date. i.e… Dinner, drinks a movie etc…
However, meeting some girl at a bar then two or three hours later going home and having sex doesn’t count as an actual date. A girl like that I would NOT consider as a GF.
Not that I’m judging. If guys can do it with impunity so should women. For me it’s just the awkwardness of a one night stand that makes it hard for me to look that girl in the eye again. Kind of silly I guess.
I’m done with one night stands. (I think)
I probably wouldn’t have had sex with her at all if she wasn’t GF material (though I can’t guarantee that). First date, second date, tenth date… doesn’t change a thing. Except if I begin to suspect she’s playing “hard to get” on purpose, or generally playing games, but that would rather be the opposite of your situation.
But as a poster already stated, you can’t generalize. Each man is different.
I am not sure that sex is the predictor I would go with.
It’s so early days in this relationship and maybe you didn’t understand that he really (really) meant it when he said he was the world’s number one Monkees fan, or missed his foreshadowing of the temper or complete lack of table manners/humor/taste in music. Those, more than sex, are usually the kind of things that will determine whether the relationship is going to stand or fail, and sex early on can make you feel more invested in the relationship than you might otherwise & stick out a bad match too long or blind you to how annoying you find it when he wear a Turtleneck and hums DayDream Believer tinkering around the house.
That is why sex that early on* could* be a bad idea, and not because you didn’t wait for the calendar page to flip or the clock to strike 12 or follow some unwritten “rules” before hitting the sheets.
Just my $0.02
Not in the slightest.
To me it wouldn’t be directly relevant to the issue, except in that it might answer questions of attraction, desirability, desire levels and other sexual compatibility issues which might factor into the ‘long term relationship’ question.
For example: Say I go out with a woman who proceeds to initiate sex on the second date. So far, she seems to be into me and we’re both interested. But then I find that she’s not very clean (a serious turn off) and is both passive and uninteresting in bed. Or that maybe, underneath her clothing, she has a serious sexual deformity that squicks me out.
THAT would make me immediately discard her as a viable long-term relationship partner right there.
I could come up with other examples that might lead to other conclusions, but you get the idea. The only real difference it would make is that it answers certain questions sooner rather than later.
I’ve never seen a willingness to have sex with me as a problem in a relationship.
Me neither. I had sex with my fiancee within a few hours of meeting her. Seven years later, we’re getting married (in 2 weeks).
Why is when you have sex supposed to be such a big deal? As long as you enjoy it when it happens and you’re compatible, why feel the need to wait?
I wouldn’t generally push for sex by the second date, so I’m the opposite of SHAKES. If we ended up sleeping together that soon, it would have to be at her insistence, so I have no advice that’s helpful here. If that’s any use.