This study evaluated the effects of interactive voice response (IVR) system reminders to managed care organization (MCO) members to obtain mammograms, Papanicolaou (Pap) tests, and influenza immunizations. The MCO identified 3 member cohorts and sent IVR reminders to get preventive services. Analyses employed claims data to examine relationships between IVR reminders and preventive service use 5 to 9 months post-intervention among members without prior utilization. Multivariate logistic regressions controlling for age, gender (for influenza immunizations), and risk stratum confirmed hypothesized relationships between intervention and preventive services: mammograms, odds ratio (OR) = 1.263 (95% confidence interval [CI] = 1.104, 1.444); Pap tests, OR = 1.241 (1.107, 1.391); influenza immunizations, OR = 2.072 (1.665, 2.580). IVR reminders are associated with higher rates of mammograms, Pap tests, and influenza immunizations. Study limitations include unknown generalizability of results and possible self-selection. There is justification for more IVR interventions and research to enhance MCO members' preventive service utilization.