A multidimensional work-sampling technique was used to quantify a pharmacokinetics resident's duties. Four dimensions were measured: activity, contact, function, and location. A code list of 47 variables was developed to encompass all activities of the resident being observed. A combination of self-reporting and observer reporting was used to test the veracity of the resident's report and to determine whether differences in reporting occurred. Observation was done 20 times a day over a five-week period (24 working days). Random time periods separated the observation points. The observer and the resident recorded 260 and 220 observations, respectively, for a total of 480. The overall reliability measure was 78%, indicating good interobserver agreement. The resident spent about 36% of his time doing work related to pharmacokinetics consultations and 23% of his time attending meetings. He spent a large proportion of time (48.5%) working alone. Much of his remaining time was spent with the Pharm.D. students and the preceptors. Multidimensional work sampling based on a combination of self-reporting and observer reporting is a useful tool for quantifying the work practices of pharmacokinetics residents.