- Studies of treatment efficacy are important for the development of cancer chemoprevention strategies. Recruitment aims for motivated, compliant subjects. The Concerned Smoker Study targets smokers with at least a 15-pack-year history and bronchial atypia on sputum sampling. Subjects receive etretinate 25 mg daily or identical placebo and are followed for 6 months. Compliance was monitored by assessing timely return for follow-up visits, return of monthly sputum samples, pill counts, and serum etretinate levels. Contamination, in the control group, was assessed by measuring etretinate levels. With half of the subjects having completed the study, this report assesses compliance: 88% follow-up visits occurred on schedule with only 9 missed visits of a possible total of 380; 443 (97.1%) of 456 possible sputum samples were returned. Pill counts indicated a high degree of compliance which was supported by the serum etretinate levels. Contamination was insignificant. The results suggest a very high degree of compliance. Only minor protocol changes will be required.