Pilot studies are an essential component for major chemoprevention trials. Prior to initiating the multicenter Carotene and Retinol Efficacy Trial to assess the effectiveness of beta-carotene and retinol for preventing lung cancer, we conducted pilot studies in Seattle between 1985 and 1988 in two high risk populations: current and former heavy smokers and asbestos-exposed workers. The Asbestos Workers Pilot Study for the Carotene and Retinol Efficacy Trial demonstrated that recruitment of asbestos-exposed participants with relevant risk factors was feasible from identified sources. We documented negligible toxicity and high adherence with the protocol, schedule, and intervention. Results from the pilot led to extension of the placebo run-in period, changes in the eligibility criteria, improvements in recruitment strategies and scheduling, elimination of stratification by risk factors in randomization, modifications of study vitamin dosage and of side effects monitoring, and refinement of trial design parameters for Carotene and Retinol Efficacy Trial. The Smokers Pilot is reported in the accompanying article (G. E. Goodman et al., Cancer Epidemiol., Biomarkers & Prev., 2: 389-396, 1993).