To evaluate trends over time in incidence of specific types of cancer in the HIV-infected population, we used multivariable Poisson regression in a model controlling for age (15 to 34 years, 35 to 59 years, ≥60 years), race (white, black, other), sex, HIV risk group (men who have sex with men vs. other), nadir CD4 count (<0.200 × 109 cells/L, 0.200 to 0.499 × 109 cells/L, ≥0.500 cells/L), and antiretroviral therapy (any vs. none). The linear trend denotes the estimated average change in incidence rate from pre-HAART to early HAART and from early to recent HAART. To evaluate trends over time in the incidence of a specific type of cancer in the SEER population, we used a weighted multivariable Poisson regression to assess linear trends in a model weighted according to the age, race, and sex distribution of the combined ASD Project and HOPS population. To determine whether cancer incidence in the HIV-infected population changed over time relative to the general population, we included a 2-way interaction term between trend and study sample in the multivariable model. To describe factors associated with each type of cancer among HIV-infected persons, we used multivariable Poisson regression, including the covariates as already defined for linear trend, age, race, sex, HIV risk group, nadir CD4 count, antiretroviral use, and hepatitis B or C infection (liver cancer only). We chose these covariates because they had a known association with cancer or were markers of immune function, and we adjusted for them simultaneously.