The physical, psychological and social consequences of alcohol abuse remain a critical health problem. Every year in Australia, excessive consumption is responsible for 3,000 - 6,000 deaths and costs the community $6 billion. Approximately 15% of Australians abuse alcohol and 5% of men and 3% of women are alcohol dependent (addicted to alcohol). Better treatment for alcohol dependence is urgently needed. Treatment for alcohol dependence remains unsatisfactory. Most treatments lead to abstinence in only 1 out of 3 cases, and approximately 50% of these will relapse within 3 months of completing treatment. Two drugs (naltrexone and acamprosate) appear to interfere with the effects of alcohol on the brain that promote addiction. There is evidence that both drugs are beneficial in the treatment of alcohol dependence and both are now available in Australia. At present, no data have been reported comparing the effectiveness of these two drugs. The proposed project will compare naltrexone and acamprosate in a large, carefully performed, study. The study will help determine which subjects are likely to benefit from one or the other of these agents.