This study evaluated differences in sexual behavior and risk for sexually t
ransmitted diseases (STDs) among men who have sex with men (MSM) who met th
eir partners on-line and those who did not. A self-administered questionnai
re on sexual behavior was offered to a convenience sample of patients seeki
ng public STD services. Thirty-two percent of MSM patients reported meeting
a sexual partner over the Internet in the past year. MSM with on-line part
ners were younger, more likely to report sex with an HIV-positive person in
the last year, and more likely to report casual partners in the last year
compared with MSM with only off-line partners. HIV-negative MSM with on-lin
e partners were more likely than HIV-negative MSM with only off-line partne
rs to have received money or drugs for sex in the past year and to report s
ex with an HIV-positive partner in the past year. Although meeting partners
on the Internet was common and associated with increased risk for STDs in
MSM, it also presents new untapped opportunities for on-line health promoti
on and disease prevention.