In Peru, an evaluation of 20 health centers and 40 community oral rehydration units (CORUs) in southern Lima and the Sullana region (northern Peru) was done to determine the number of diarrhea cases attended by CORUs, the knowledge of the volunteers in charge, and the quality of care provided by these services. Data were collected during April-May 1991, in the middle of the cholera epidemic in Peru. 80% of health centers and 79% of CORUs had oral rehydration salts (ORS) available. 63% of these health centers stored the ORS sachets appropriately compared to just 48% of the CORUs. Health professionals caring for diarrhea cases at health centers included auxiliaries (40%), physicians (34%), and nurses (17%). Most of the CORUs (61%) were in an urban area. Urban CORUs were closer to the nearest health center than rural CORUs (1 vs. 3 km; p = 0.003). The close proximity of urban CORUs to health centers works against the CORU strategy to improve coverage of diarrhea cases and access to ORS. Almost all diarrhea cases at the CORUs had no signs of dehydration, but most received ORS solution anyhow. In fact, only 10% of CORU volunteers and 7% of health workers at the centers looked for key signs of dehydration. A CORU volunteer even referred such a case (a child) to the next level. 85% of volunteers knew how to manage complications, while just 55% of health professionals did. Few volunteers and health professionals recommended breast feeding during a diarrhea episode (38% and 41%, respectively). About 25% of both groups knew about proper dietary management. The low knowledge levels suggest failures in training activities. Only 48% of CORUs received supervision from health center based health professionals the during the last month. CORUs did not maintain records of CORU activities (e.g., number of ORS sachets distributed) which made it difficult to monitor and evaluate the performance of CORUs.