The number of dispensing doctors has increased in the last decade, but the implication of this trend on the quality of health care and drug use is unknown. We present a comparative drug utilization study of 29 dispensing doctors and 28 non-dispensing doctors in Zimbabwe based on standard indicators developed by the World Health Organization. Dispensing doctors prescribed significantly more drugs per patient than non-dispensing doctors (2.3 versus 1.7), injected more patients (28.4% versus 9.5%), and prescribed more antibiotics (0.72 versus 0.54) and mixtures (0.43 versus 0.25) per encounter. Dispensing doctors also spent significantly less time on each encounter (8.7 min versus 13.0 min) than their non-dispensing colleagues. The use of generic name, brand name and essential drugs did not differ significantly between the two groups of practitioners. Multivariate analyses controlling for gender, race, place of education, location of practice and patients seen per day showed that dispensing by doctors was associated with less clinically and economically appropriate prescribing. These findings suggest that the quality of health care--as related to drug use, patient safety and treatment cost--is lower with dispensing doctors than with non-dispensing doctors.