Integrated Management of Childhood Illness (IMCI) is a child health strategy in developing countries with a goal of improving the treatment of illnesses at first-level health facilities through the use of clinical practice guidelines. The World Health Organization (WHO) recommends implementing the guidelines with an 11-day training course. There is a concern that health workers might not master all aspects of the guidelines and that health worker performance may deteriorate over time. In 1999, Benin (in West Africa) was planning to implement IMCI. In response to concerns about how well health workers would follow IMCI guidelines, interventions were designed to support health workers after IMCI training: 1) regular supervision of health workers; 2) supervision of supervisors; 3) job aids; and 4) non-financial incentives for health workers. These interventions were intended to be used together. The objective of this study was to determine the effectiveness and cost-effectiveness of the package of interventions to support IMCI-trained health workers in Benin.