BACKGROUND: Human immunodeficiency virus (HIV)-infected patients are at higher risk of malignancies. In addition to traditional determinants, a specific deleterious effect of HIV and immunodeficiency is speculated. We aimed at studying the association between immunological and virological characteristics of HIV-infected patients in care and the risk of acquired immunodeficiency syndrome (AIDS)-defining and non-AIDS-defining malignancies. METHODS: Patients consecutively enrolled in the hospital-based Agence Nationale de Recherche sur le Sida (ANRS) CO3 Aquitaine Cohort were included if the duration of follow-up was >3 months during the period 1998-2006. Multivariate modeling used an extended Cox proportional hazards model for time-dependent covariates and delayed entry. RESULTS: The 4194 patients included in the study developed 251 first malignancies during 22,389 person-years. A higher incidence of AIDS-defining malignancies (107 cases) was independently associated with (1) both longer and current exposures to a plasma HIV RNA level >500 copies/mL (hazard ratio [HR], 1.27 per year [P<.001] and 3.30 [P<.001], respectively) and (2) both longer and current exposure to a CD4(+) cell count <200 cells/mm(3) (HR, 1.36 per year [P<.001] and 6.33 [P<.001], respectively). A higher incidence of non-AIDS-defining malignancies (144 cases) was independently associated with longer and current exposure to a CD4(+) cell count <500 cells/mm(3) (HR, 1.13 per year [P=.01] and 2.07 [P<.001], respectively) and male sex (HR, 1.69; P=.02) but not with plasma HIV RNA level (P=.49 and P=.10 for cumulative and current exposures, respectively). CONCLUSIONS: Uncontrolled plasma HIV RNA level was independently associated with a higher likelihood of developing AIDS-defining malignancies, whereas immunosuppression was associated with a higher risk of developing any type of malignancies. Antiretroviral treatment should aim at reaching and maintaining a CD4(+) count >500 cells/mm(3) to prevent the occurrence of malignancy, this should be integrated to malignancy-prevention policies.