Among men who have sex with men (MSM) in Los Angeles County, methamphetamine use is associated with high rates of HIV prevalence and sexual risk behaviors. In four separate samples of MSM who differed in the range of their intensity of methamphetamine use, from levels of recreational use to chronic use to those for MSM seeking drug abuse treatment, the association between methamphetamine use and HIV infection increased as the intensity of use increased. The lowest HIV prevalence rate (23%) was observed among MSM contacted through street outreach who mentioned recent methamphetamine use, followed by MSM who used at least once a month for six months (42%), followed by MSM seeking intensive outpatient treatment (61%). The highest rate (86%) was observed among MSM seeking residential treatment for methamphetamine dependence. The interleaving nature of these epidemics calls for comprehensive strategies that address methamphetamine use and concomitant sexual behaviors that increase risk of HIV transmission in this group already at high risk. These and other data suggest that MSM who infrequently use methamphetamine may respond to lower intensity/lower cost prevention and early intervention programs while those who use the drug at dependence levels may benefit from high intensity treatment to achieve goals of reduced drug use and HIV-risk sexual behaviors.