The proportions of time pharmacists spent in professional and nonprofessional activities is compared under alternative staffing arrangements. Daily activities were observed in three pharmacy satellites each serving approximately 100 beds of a 730-bed hospital. Ten pharmacy administrators and residents recorded more than 8000 observations over a 14-day period, 24 hours per day. In each observation, basic functions were noted; these were chosen from a list compiled to include all pharmacy activities. A specific staffing pattern was identified in each observation. The observations were then categorized as professional or nonprofessional activities as predefined by the majority of the pharmacy staff. As staffing patterns varied, significant differences occurred in the ratio of professional to nonprofessional activities. The greatest percentage of professional activity was observed when one pharmacist worked with more than one technician; where the staffing pattern contained more pharmacists than technicians, a smaller percentage of the pharmacists' time was used in professional activity. Overall, pharmacists were engaged in activities considered professional in 52% of the observations. Assuming that the most efficient use of pharmacy personnel involves a high ratio of professional to nonprofessional activity in the pharmacists' workload, the optimum staffing arrangement would include at least the same number of technicians as pharmacists. Factors other than staff mix affect efficient management of pharmacists' professional time.