We examined the relationship between patterns of alcohol consumption and health care costs among adult members of the Kaiser Permanente Medical Care Program (KPMCP) in Northern California. A telephone survey of a random sample of the KPMCP membership aged 18 and over was conducted between June 1994 and February 1996 (n=10,175). The survey included questions on sociodemographic characteristics, general and mental health status, patterns of past and current alcohol consumption; inpatient and outpatient costs were obtained from Kaiser Permanentes cost management information system. Results showed that current non-drinkers with a history of heavy drinking had higher health costs than other non-drinkers and current drinkers. The per person per year costs for non-drinkers with a heavy drinking history were $2421 versus $1706 for other non-drinkers and $1358 for current drinkers in 1995 US dollars. A history of heavy drinking has a significant effect on costs after controlling for sociodemographic characteristics, health status and health practices. Current drinkers have the lowest costs, suggesting that they may be more likely than non-drinkers to delay seeking care until they are sick and require expensive medical care.