Paper provides a survey of the basic knowledge on the genetic polymorphism of enzymes involved in the metabolism of medicinal drugs and other xenobiotics. The major implications of this phenomenon have been described, namely the interindividual variability in the therapeutic effect of drugs differently metabolised by the polymorphically determined enzymes, or the interindividual variability in the susceptibility to neoplastic processes related to the polymorphically determined enzymes metabolising xenobiotics. Recent advances in the understanding of the molecular genetics of enzymes metabolising drugs and other xenobiotics (particularly cytochrome P-450, glutathione S-transferase, N-acetyltransferase, UDP-glucoronosyltransferases and others), help to understand the molecular basis of several genetic polymorphisms. Present article reviews the current status of studies on polymorphism of xenobiotics-metabolising enzymes and brings a discussion to their pharmacotherapeutical relevance and to their significance for identification of susceptible individuals/subgroups in the carcinogen exposed population.

        Key words: genetic polymorphism, interindividual variability in the therapeutic response, variability in the cancer susceptibility, xenobiotics, cytochrome P-450