The types of activities performed by four clinical pharmacy residents and the amount of time spent on each activity were studied using a workload measurement system. A workload measurement system was developed to record all activities performed by pharmacy residents. The system included 50 activities that were grouped under 11 general headings; residents' time was divided among 10 major areas of service. The following data were collected and analyzed each month during the six-month study period: units of work, weighted units of work, total productive hours, total service hours, and productivity. The residents participated in 39 of 50 clinical pharmacy activities. Activities performed most frequently included nursing-home-care-unit drug reviews, drug monitoring, and rounds. The most time-consuming activities were clinical education, administration, and drug-use review. Productivity ranged from 80 to 115% and was influenced by residents' assigned rotations. A workload measurement system for quantifying the time spent by residents performing various clinical pharmacy activities provided objective data that were used to restructure a clinical pharmacy residency program.