Recently, an association has been reported between schizophrenia and a rare allele containing 10-repeats (A10) of a polymorphic tetranucleotide motif in the first intron of the tyrosine hydroxylase (TH) gene. The present association analysis tested the hypothesis that the A10 candidate allele confers vulnerability to alcohol-withdrawal delirium with visual hallucinations. The genotype of the TH tetranucleotide polymorphism was assessed in 204 German controls and 311 German alcohol-dependent subjects, including 63 alcoholics with a history of visual hallucinations during withdrawal delirium. The frequency of the A10 allele was significantly increased in the alcoholics with withdrawal delirium (3.2%) compared with that in the controls (0.5%; Fisher's exact test: P = 0.03, two-tailed; OR (A10+) = 6.85, 95% confidence interval: 1.52-30.79). The possible allelic association suggests that allelic variation at the TH locus mediates vulnerability to alcohol-withdrawal delirium in a small proportion of alcohol-dependent subjects.