As part of an evaluation of the effects of the computer-stored ambulatory record (COSTAR) on clinic function, a resident teaching clinic was divided into a study group with access to COSTAR and a control group allowed access only to conventional medical records. Staff attitudes toward use of the computer were sampled and detailed time studies of clinic patient flows were performed. Staff attitudes reflected a high degree of acceptance, favoring COSTAR over conventional records. This was primarily related to improvement in telephone management and demand care. House staff never became facile users of COSTAR because of infrequent clinic sessions. Clinics assigned to COSTAR experienced somewhat longer waiting times due to an increased workload and training effects. Installation of computerized records should prompt a careful evaluation of expected benefits.