The study reports the impact of a computer-based drug profile upon physicians' drug order recording behaviors. The drug profile system, including information about both drugs ordered and prescriptions received, was implemented for a randomly selected group of Kaiser Foundation Health Plan members during 1973. The monthly updated profile was made readily accessible to physicians. Drug order notations entered by physicians on outpatient medical records were examined to determine if the availability of the profile influenced the completeness of drug-related data being recorded by physicians. Using an experimental design, the results indicated the availability of the profile did not influence the completeness of drug-related data recorded. Also, observation of the data generated for analysis suggests caution in assuming drug notations or prescriptions reflect complete and reliable drug use data.