Quality assurance sampling techniques with small samples offer a method of monitoring performance of health services in small health areas, and of identifying areas with poor performance in which remedial actions need to be targetted. Lot Quality Assurance Sampling methods were used to assess the coverage resulting from three immunization campaigns in rural and urban areas in the mountains of Peru. Application of these methods in 12 health areas with populations of 538 to 15 780 by Ministry of Health personnel proved feasible and could be used to identify areas with poorer vaccination coverage. Further discussion about possible reasons for poor coverage led to corrective actions in these health areas and an improvement in overall coverage from 78% to 88% in a three-month period. These quality assurance methods are a useful supervisory tool to improve health programme performance. © 1990 International Epidemiological Association.