A multi-country evaluation is being carried out in Brazil and four other countries to determine the effectiveness, cost, and impact of the Integrated Management of Childhood Illness (IMCI). We examine the effect of IMCI on the quality of health care provided to children under five visiting health facilities. A health facility survey was conducted at 24 facilities (12 with IMCI) in each of four States in the Northeast. We assessed the quality of care provided to children between 2 months and 5 years attending the facilities. Health workers trained in IMCI provided significantly better care than those not trained. Significant differences between health workers who were trained or not trained in IMCI were found in the assessment of the child, disease classification, treatment, and caretaker communication. Nurses trained in IMCI performed as well as, and sometimes better than, medical officers trained in IMCI. We conclude that while there is room for further improvement, IMCI case management training significantly improves health worker performance, and that parts of Brazil that have not yet introduced IMCI should be encouraged to do so.