Mutations in the CYP1A1 gene were investigated in 324 Polish children and adolescents using PCR/RFLP. Mutation T6235C (m1) occurred in 6.6% of alleles (95& confidence limits 4.8%-8.8%); A4889G (m2), 2.2% (1.2%-3.6%); and C4887A (m4), 2.0% (1.1%-3.4%). T5639C (m3) was not detected. Wild-type allele CYP1A1*1 was found in 91.4% (88.9%-93.4%). In all cases of theoretically possible mutation linkages, the novel method of allele specific polymerase chain reaction-clamping mediated by peptide nucleic acids was applied to define allelic allocation. All 14 individuals with an m2 mutation also had m1 on the same allele (CYP1A1*2B). Allele CYP1A1*2A, carrying only m1, appeared in 4.5% (3.0%-6.4%). In the single case of m1/m4, these mutations were placed on distinct alleles. CYP1A1 mutations in the Polish sample tended to be less frequent than in other Caucasian groups.