In 237 male inpatients with alcohol dependence, clinical, demographic and biochemical data were analyzed in relation to alcohol tolerance. All subjects had a history of marked tolerance. At the time of assessment, 46% of subjects continued to meet the criteria for marked tolerance and 54% of the subjects reported a loss or decreased tolerance. Subjects with decreased tolerance were older than those with high tolerance and had a longer duration of illness. The age of onset was similar in both groups. Patients with decreased tolerance had more mental confusion and psychotic symptoms, and were less likely to be currently married.