In the period 1977-1979, a sample of consecutively admitted alcoholic in-patients was studied with CT scan of the brain and neuropsychological tests. A subsample of 52 patients met the following criteria: age less than 46 years, no history of severe head injury or focal signs of traumatic brain damage, and no history of liver disease, drug abuse, or long-lasting anticonvulsant therapy. However, 72% of the patients showed brain atrophy and 49% intellectual impairment as compared to 16% and 13%, respectively, in an age-matched sample of men from the general population. Five years later, after excluding patients with head trauma, serious alcoholic liver disease and drug abuse, 37 patients were reinvestigated. Sixteen patients were abstinent or had greatly improved drinking habits during the 5-year follow-up period and 21 were still drinking. Alcohol abstinence was found to be associated with a regress of cortical atrophy and central atrophy as assessed by the width of the 3rd ventricle. However, the recovery was not complete as compared with the prevalence of atrophy in the sample from the general population. Among the patients a significant improvement in one cognitive test and a trend to improvement in some other tests associated with improved drinking habits was observed. Regression of central atrophy as assessed by a decreased diameter of the 3rd ventricle was associated with improvement in the very same cognitive tests. The results suggest that both atrophy of the brain and cognitive ability can improve in alcoholics who give up drinking.(ABSTRACT TRUNCATED AT 250 WORDS)