Reelz Channel has an article from when they interviewed Robert Pattinson and Taylor Lautner during Comic Con!

Screaming teenage girls everywhere will be happy to know that Edward and Bella do indeed swap spit in the Twilight movie, albeit briefly. “There’s only really one time,” says Pattinson. “The more Bella says ‘I’m not scared of you, you’re not a monster’ the more I believe it. I kind of forget that I am a vampire and what my actual instincts are. I try and kiss her and it ends up being a nightmare. She has a sort of hormonal rush and I have the ‘I want to kill you’ rush.  It ends up being quite sexy though in a weird sort of way.”