Bufuralol is a beta-adrenoceptor blocking drug whose metabolism is under the same genetic control as debrisoquine. Bufuralol appears to be a sensitive tool for characterization of this pharmacogenetic variation. After test drug absorption, one single blood collection allows separation between extensive and poor metabolizers. In Switzerland, the poor metabolizer status has a prevalence of 8%. In poor metabolizers bufuralol plasma concentrations are very high, an observation of interest when considering the occurrence of side effects of the drug. In addition to disease-induced variability in drug response, oxidation polymorphism is a major source of interindividual variations in drug effect. As the metabolism of numerous drugs is affected by this pharmacogenetic variation, the question arises whether systematic screening should not be considered.