In this study new methods for the detection of two polymorphic sites in the GSTP1 coding region have been developed. Both sites are polymorphic in several racial groups and there are significant differences between groups, in the gene frequency at each site. Although previous studies of recombinant GSTP1-1 have suggested that there are significant differences in the specific activity and stability of the I105 or V105 isoforms, no differences in the distribution of GSTP1-1 activities in normal blood donors with different GSTP1 genotypes were detected in this study. These data were obtained with CDNB as a substrate and greater differences may be apparent with different substrates. The structure and organization of the GSTT2 gene was also investigated and a pseudogene that occurs at a polymorphic frequency in European Australians was discovered. This pseudogene can be detected by PCR/RFLP analysis.