OBJECTIVE: To compare and evaluate drug notations in outpatient medical records and in pharmacy records in a cohort of HIV-1-infected patients treated with antiretroviral drugs. METHODS: Data on 103 patients were obtained from January 1, 1998, through December 31, 1999, by medical chart review and collection of pharmacy records. Two analyses were performed. First, antiretroviral drugs and comedication in the pharmacy records were documented and compared with their appearance in the outpatient medical records. Second, a detailed comparison was performed at 5 time points during the study period for the antiretroviral drugs. Generic name, formulation, strength, and frequency of dosing as registered in the outpatient medical records were compared with those registered in the pharmacy records. RESULTS: Total drug dispensation was 1607 (366 and 1241 antiretroviral drugs and comedication, respectively). The first screening resulted in a total discrepancy of 55.1% (n = 885), of which 97.1% (n = 859) was attributed to the comedication and 2.9% (n = 26) to the antiretroviral drugs. The discrepancy for the antiretroviral drugs at the specific time points ranged from 5.1% to 12.6% when the generic name only was used, and from 7.1% to 17% when formulation, strength, and frequency of dosing were also taken into account. CONCLUSIONS: The observed discrepancy between outpatient medical records and pharmacy records mainly concerns the comedication. For the antiretroviral drugs fewer, but still substantial, discrepancies were observed. These results indicate that full exchange of information conceming drug use in this population between general practitioners and specialists (infectious disease) is lacking.