In the central nervous system, cholecystokinin (CCK) is an important neurotransmitter that gives the influences on firings, anxiety, notiception, and dopamine-related behavior. CCK co-exists in the dopaminergic neurons, interacting with dopamine. In this study, we examined the genetic variant -45 C to T substitution of the CCK gene promoter region among 195 healthy Japanese and 174 patients with alcohol withdrawal syndrome (52 delirium tremens, 39 hallucinosis, 20 seizures, and 92 lack of these symptoms) by using polymerase chain reaction-based single-strand conformational polymorphism analysis. Patients with delirium tremens showed a significantly higher frequency of the variant, compared with the controls (chi2 = 4.91, p < 0.03), but patients with other symptoms showed no difference. These data suggested that the individuals possessing allelic mutation (-45T) in the promoter region of the CCK gene might be susceptible to delirium tremens caused by alcohol abuse.