Monitoring the incidence of human immunodeficiency virus (HIV) infection among men who have sex with men (MSM) is imperative for developing targeted prevention programs and evaluating their effectiveness. The authors used California counseling and testing data to estimate the temporal trend in HIV incidence among MSM in California. HIV incidence rates were retrospectively calculated among MSM who had received at least 1 HIV test at a public California counseling and testing site between 1997 and 2007 and had a prior HIV-negative test from any HIV testing source. All study subjects were weighted on the basis of the interval between the last HIV-negative test and the current HIV test to account for the right-truncation bias introduced by more frequent testers. The authors observed that the HIV incidence rate among MSM in California increased from 2.0/100 person-years (95% confidence interval (CI): 1.8, 2.2) in 1997 to 2.4/100 person-years (95% CI: 2.2, 2.6) in 2003 and then decreased to 1.9/100 person-years (95% CI: 1.7, 2.0) in 2006. Trend analyses showed that both the increase (P < 0.001) and the decrease (P < 0.01) were statistically significant. The study showed that HIV incidence among MSM in California had decreased since 2003.