A small proportion of alcohol-dependent men and women experience delirium tremens (DTs) and/or convulsions during alcohol withdrawal. While some characteristics of individuals most likely to show these severe sequelae of the abstinence syndrome have been described, it is not clear whether these risk factors operate independently in their association with severe withdrawal. The Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA) interview was used to evaluate 1648 alcohol dependent men and women (including 540 women). The background characteristics and drinking histories of the 160 men and 51 women (12.8% of the subjects) who reported ever having had at least one episode of DTs and/or convulsions during withdrawal were compared with the characteristics of the remaining alcohol dependent individuals. Compared to other alcohol-dependent subjects, those with histories of severe withdrawal reported a greater maximum number of drinks in any 24-hour period (40.9 +/- 25.71 versus 24.9 +/- 17.72), more withdrawal episodes (28.2 +/- 33.74 versus 15.9 +/- 26.84), more non-medicinal use of sedative-hypnotics (56.4% versus 32.9%) and a greater number of medical problems. Hierarchical logistic regression analysis revealed that the most powerful differences between those with histories of more and less severe withdrawals related to the maximum number of drinks per day and the total number of withdrawal episodes. The remaining variables still added significantly to the relationship to more severe withdrawal. The etiology of DTs and convulsions is complex and involves the interaction of diverse characteristics representing relatively unique domains. It is hoped that these data will help clinicians identify individuals most likely to have experienced severe withdrawal syndromes and will aid researchers attempting to understand more about the etiology of these problems.