400 ﬁnd sex partners in the past 6 months; this difference was only statistically signiﬁcant between MSM and heterosex- ual men and between MSM and women (v2 = 15.82, P \ 0.001 and v2 = 15.64, P \ 0.001, respectively). There were no differences in reported Internet use to ﬁnd sex partners between participants based on clinic site or by income category in any gender/orientation group. Younger participants were more likely to report going online to ﬁnd sex partners than older participants (51% of participants less than 30 years old vs. 18% of participants 55 years old or older, v2 = 28.83, P \ 0.001) (Fig. 2b). The most commonly used sexual networking sites were Craigs- list.com (47%), Manhunt.net (41%), adam4adam.com (39%), men4now (33%), and gay.com (11%). Compared to participants who did not report going online to ﬁnd sex partners, those who reported going online to ﬁnd sex partners reported a higher median (IQR) number of sex partners in the past 6 months (4 (3–9) vs. 1 (0–1), z = -11.47, P [ |z| = 0.00) and were more likely to report having unprotected sex sometimes, often or always (32 vs. 10%, v2 = 42.13, P \ 0.001). Among MSM, participants who reported methamphetamine use in the past 12 months were more likely to report going online to ﬁnd sex partners in the past 6 months than those who denied methamphet- amine use in the past 12 months (55 vs. 27%, v2 = 31.22, P \ 0.001). Of those who reported using methamphet- amine in the past 12 months, 17.2% reported obtaining methamphetamine through persons met online sometimes, often or always. Of those who reported using metham- phetamine in the past 12 months, and going online to ﬁnd sex partners, 29.6% reported obtaining methamphetamine through persons met online. Discussion This study found that a substantial proportion of HIV- infected patients in medical care continue to use metham- phetamine and methamphetamine use was associated with high-risk sexual behavior and the use of sexual networking sites on the Internet. As in our prior studies, metham- phetamine use was the most common among white MSM and was more common among MSM at the County clinic than at the University clinic [9, 24]. However, that asso- ciation appeared to be related to income status. The fre- quency of methamphetamine use in the past year among our study population in 2008 (31%) was similar to the frequency found among similar samples in 2004 (35%) and 2006 (33%), and was substantially higher than the reported frequency of methamphetamine use in the past year nationwide (0.6% in 2005) [1] and in community samples of MSM in San Francisco (i.e. 9.0% of HIV-uninfected MSM and 19.9% of HIV-infected MSM in 2006) [28]. We 123 AIDS Behav (2012) 16:396–403 found that 11% of women and 26% of transgender par- ticipants reported methamphetamine use in the past 12 months. Those ﬁndings are limited by the small sample sizes of women and transgender participants; metham- phetamine use within these subgroups may warrant further study. Our results further conﬁrmed the strong association between methamphetamine use and risky sexual behavior among MSM. We found that MSM who reported meth- amphetamine use in the past 12 months reported signiﬁ- cantly increased numbers of sex partners and unprotected sex, which is consistent with other studies [3, 4, 29–32]. Interventions that target methamphetamine use in this population may be an important part of the effort to stem the ongoing transmission of HIV. We found that among HIV-infected patients seeking care, reported use of sexual networking sites on the Internet to ﬁnd sex partners was more common among MSM than non- MSM and among younger versus older participants, and that such behavior was associated with more reported sex part- ners, higher prevalence of reported unprotected sex, and higher prevalence of reported methamphetamine use. These ﬁndings are consistent with studies conducted in HIV- uninfected populations [18–22]. The frequency of reported use of sexual networking sites on the Internet among HIV- infected MSM in our study (36%) was similar to the fre- quency in another study among HIV-infected men in Atlanta, GA (37%) [33]. A larger study of men who use the Internet to seek sex with men found that HIV-infected men had a higher risk of unprotected anal intercourse with male partners than HIV-uninfected men [34] which may indicate that participants in our study who reported using sexual networking sites to ﬁnd sex partners had an elevated risk of unprotected sex when compared to the general population. Only 9% of women reported using sexual networking sites to ﬁnd sex partners; this is signiﬁcantly lower than the results of a 2004 online survey that found that 43% of female respondents used the Internet to ﬁnd sex partners and this was associated with an increased incidence of STIs and unpro- tected sex [35]. While the two study populations clearly differed and our sample size was small, the use of the sexual networking sites by women may warrant further investiga- tion. In addition, despite a small sample size, 16% of trans- gender participants in our survey reported using sexual networking sites to ﬁnd sex partners; this too may be a population whose Internet use should be investigated further. While we found that using sexual networking sites was associated with HIV-transmission risk behavior and meth- amphetamine use, the Internet also presents an important opportunity for risk-reduction interventions relating to methamphetamine use and sexual behavior. Only 3% (N = 4) of participants who reported having been in a methamphetamine treatment program reported referral to