The objective of this study was to measure how primary care family physicians perceived their own and pharmacists' contributions to medication processes as pharmacists become integrated into primary care group family practices. The 22- item Family Medicine Medication Use Processes Matrix was mailed to physicians in seven sites at the 3rd, 12th and 19th month of pharmacist integration. Paired sample t-tests for the third month results were conducted to compare perceptions between pharmacist and physician contributions. One way repeated measure ANOVA test was conducted to determine significant changes over time. Physicians initially perceived their own contributions to be significantly higher than pharmacists in three subscales: Diagnosis & Prescribing, Monitoring and Administration/Documentation and their own contributions to be significantly lower than the pharmacists in the Education subscale. Over time, physicians perceived increases in the pharmacists' contribution to the Diagnosis & Prescribing, Monitoring and Medication Review subscales and decreases in their own contribution to the Diagnosis & Prescribing and Education subscales. Changes in family physicians' perceptions of pharmacists' contribution demonstrate an initial underestimate of pharmacists' role in primary care family practice and a gradual recognition of expertise and competence. This may have led to increased comfort in sharing aspects of contribution to medication use processes.