Certain anticonvulsant drugs require N-acetylation as a major route of metabolic clearance. Single point mutations of the polymorphic N-acetyltransferase gene (pNAT) are the primary cause for impaired drug acetylation. Pharmacokinetic parameters are altered in slow acetylator phenotypes and this may compromise drug safety. Genetic analysis of allelic frequencies of individual pNAT genotypes point to significant increases in carriers of the S1/wt and S3/wt (P < 0.05) allele and a significant reduction in carriers of the S2/S2 (P < 0.01) allele, when control and epileptic patients are compared. Furthermore, the presumed link between the cytochrome P450 CYP2D6 polymorphism and the pathogenesis of Parkinson's disease led us to investigate, whether a similar relationship can be expected for other CNS disorders. Our findings indicate that poor metabolizers are more frequent (P < 0.05) amongst epileptic patients, when compared with a control population. An estimate of the odds ratio may suggest an increased risk [95% CI (confidence interval) 1.043-4.734] of up to 5-fold in epileptic patients carrying this mutation. This provides further evidence for a potential link between the debrisoquine hydroxylase gene polymorphism and CNS disorder and therefore warrants further study.