Like everyone else said, when you're 18 or become sexually active. When I was 16, I had thought I had either gotten pregnant, or my appendix was about to burst, so I had to go to an GYN, and they found a cyst on my ovary. Which was then taken out a few weeks later. In 2005, I had a LEEP procedure done, because I had one of the cancerous strains of HPV. Up until 2009, I went pretty regularly, mainly to get my BC rx. But I haven't been since then.....I should probably do that soon.