I personally knew I was bi before having any sexual encounters. It was in that tumultuous time, well not the average one, more of around 19. I was a late bloomer and had a really good friend (almost girlfriend) who I often had odd theological and sexual discussions with. One of these was about being gay or bisexual. After discussing at some length and identifying my innate femininity, I decided that I had the potential to be bisexual. Granted, I didn't say then and there: "I'm BI!", but I knew it was a possibility. The first time I realized I -was- was when I met a cute guy on the net who got me so sexually aroused I knew there had to be a significant reason. There was some activities to follow, but I was sure as of that moment that I was bi.