Objective: Many commonly used pharmaceuticals, such as antidepressants and neuroleptics as well as some illegal drugs, are metabolised by the cytochrome P 450 enzyme debrisoquine 4-hydroxylase (CYP2D6). Of Caucasians, 7-10% lack this enzyme, which can, upon administration of drugs in normal therapeutic doses, lead to adverse reactions and unexpected intoxication, leading in turn even to a fatal outcome in some cases. Methods: Individuals (n = 242) who had died due to intoxication by pharmaceuticals were genotyped for CYP2D6 and CYP2C19 and compared with a reference group of 281 blood donors. A single nucleotide polymorphism (SNP) method was used to identify five CYP2D6 alleles: *1 (wt), *2, *3, *4 and *6. The allele *5, a complete gene deletion, was identified by a multiplex amplification of long DNA fragments. Four CYP2C19 alleles *1 (wt), *2, *3 and *4 were also identified by SNP analysis. Results: The prevalence of the CYP2D6 poor metaboliser (PM) genotypes in individuals with fatal intoxication was lower (4.7%) than expected from the frequencies of these genotypes in the blood donors (8.5%). A significantly lower frequency Pc 0.005 (0.03 with correction according to Bonferroni) was found for the CYP2D6*4 allele among the fatal intoxication cases. The CYP2C19 genotype analyses showed the same results for the fatal intoxication cases and for the blood donors. Conclusions: The findings in this study confirm our earlier observations of a lower frequency of CYP2D6 PM genotypes in cases of fatal intoxication. To our knowledge, it has not been shown previously that intoxication victims might have a lower frequency of PMs than the general population. [ABSTRACT FROM AUTHOR]