Microcomputer assisted data management techniques, utilized in the oversight of two multiinstitutional trials for children with previously untreated acute lymphoblastic leukemia and unfavorable prognostic features, are presented. In the first study, such oversight hastened identification of unexpectedly prolonged delays, so that treatment could be successfully modified. In the second study, inferiority of one therapy was rapidly demonstrated, and after careful review that therapy was halted. Performance monitoring is discussed in terms of consideration of the overall quality of a clinical trial, namely, how complete are the data submitted and how precisely was protocol therapy administered; measurement of the quality of institutional participation, and identification of deficiencies in reporting or performance in the records of individual patients.