This retrospective study analyzes and compares the incidence of admissions for alcohol and drug (i.e.: heroin and cocaine) induced diseases to the internal medicine service of Locarno Regional Hospital (61 beds plus intensive care unit) between January 1, 1993 and December 31, 1994. Of 4038 admissions, 298 (7.4%) were related to alcoholism and drug addiction. 4.2% of all hospital days were due to alcohol abuse, whereas 3.2% were related to drug abuse (of these 1.8% were for HIV-associated diseases and 0.9% for withdrawal treatment). The male/female ratio was 3:1 in both groups, the average age of women being significantly lower in the alcoholic group (50.5 +/- 14.4 years vs. 58.1 +/- 12.9; p = 0.003). Over 90% of the patients with alcohol-induced conditions continued to consume alcohol. On the contrary, only 16% of the HIV-positive patients were still drug-addicted. The in-hospital mortality was 6% (5% in the alcoholic group; 1.6% and 12%, respectively, in the HIV-negative and HIV-positive groups of drug addicts). This study confirms the high prevalence of diseases related to alcohol and drug abuse. Women are less affected, but show complications of alcohol abuse earlier. Despite the HIV epidemic in our area, the admissions of alcoholics to the hospital are more frequent than those of drug addicts. Most of the drug addicts with an HIV-associated condition are in remission, whereas alcoholics with alcohol-induced diseases continue, for the most part, to be alcohol-dependent.