Regular intake of alcohol is associated with elevated levels of high density lipoproteins (HDL). Opinions differ, however, on the HDL subfraction which is preferentially influenced by alcohol. In the present study we measured the HDL subfraction lipid and protein concentrations and postheparin plasma lipase activities in chronic alcohol users immediately after cessation of drinking and sequentially during one week of total abstention. The HDL2 mass concentration decreased significantly already during two abstinent days the decline continuing until the 8th day. At this time the mean HDL2 concentration had decreased by 38% from the initial value (P less than 0.05). The HDL2 cholesterol, phospholipid and protein concentrations decreased in approximately similar proportions, whereas the HDL2 triglyceride increased by 40%. The HDL3 mass concentration decreased by 13% but this change was not significant. Also in HDL3 the cholesterol, phospholipid and protein contents decreased to a similar extent but the triglyceride content rose. The postheparin plasma lipoprotein lipase activity decreased by 41% and the hepatic lipase by 37% during the abstention. It is concluded that in chronic alcoholics HDL2 accounts for the major part of the increase in HDL.