BackgroundInterventions to reduce the burden of disease and mortality in sub-Saharan Africa increasingly recognize the important role that drug retailers play in delivering basic healthcare services. In Nigeria, owner-operated drug retail outlets, known as patent and proprietary medicine vendors (PPMVs), are a main source of medicines for acute conditions, but their practices are not well understood. Greater understanding of the role of PPMVs and the quality of care they provide is needed in order to inform ongoing national health initiatives that aim to incorporate PPMVs as a delivery mechanism.Objective and MethodsThis paper reviews and synthesizes the existing published and grey literature on the characteristics, knowledge and practices of PPMVs in Nigeria. We searched published and grey literature using a number of electronic databases, supplemented with website searches of relevant international agencies. We included all studies providing outcome data on PPMVs in Nigeria, including non-experimental studies, and assessed the rigor of each study using the WHO-Johns Hopkins Rigor scale. We used narrative synthesis to evaluate the findings.ResultsWe identified 50 articles for inclusion. These studies provided data on a wide range of PPMV outcomes: training; health knowledge; health practices, including drug stocking and dispensing, client interaction, and referral; compliance with regulatory guidelines; and the effects of interventions targeting PPMVs. In general, PPMVs have low health knowledge and poor health treatment practices. However, the literature focuses largely on services for adult malaria, and little is known about other health areas or services for children.ConclusionsThis review highlights several concerns with the quality of the private drug retail sector in Nigeria, as well as gaps in the existing evidence base. Future research should adopt a more holistic view of the services provided by PPMV shops, and evaluate intervention strategies that may improve the services provided in this sector.