Individual differences in xenobiotic metabolism influence the therapeutic value of many drugs and are of major concern during the development of new drug candidates. A number of polymorphic cytochrome p450 enzymes account for a significant part of this variation. A better understanding of these genetic factors would be of value for drug development, as well as clinical practice. To fulfill the goal of a personalized medicine, methods for simple and accurate assessment of cytochrome p450 genes are required. We report on the development of multiplex assays for genotyping of the cytochrome p450 drug-metabolizing enzymes CYP2D6, CYP2C9, and CYP2C19 with Pyrosequencing technology. Eleven variable positions, representing 12 of the most frequent alleles, were scored: CYP2D6 alleles *2, *3, *4, *6, *7, *8, and *14, CYP2C19 alleles *2, *3, and *4, and CYP2C9 alleles *2 and *3. Four multiplex Pyrosequencing reactions per patient sample were performed to cover these positions, using either simplex or multiplex PCR for amplification of target DNA sequences. Unequivocal genotypes were obtained for all patient samples, and the results were validated by comparing with results obtained using PCR-RFLP. For positions addressed with both methods, the results were in complete agreement. Pyrosequencing technology offers a highly automated, rapid, and accurate method for identification of cytochrome p450 alleles, which is suitable for pharmacogenomic research, as well as for routine assessment of patient genotypes.