Endogenous substances resulting from interactions between alcohol and possibly opioid metabolites and neurotransmitters (dopamine, indolamines) could be mediators of the pathochemical process towards dependence. Beta-carbolines (harman norharman) are increased in alcoholics and - according to the presented results - in heroin addicts. Psychopathological disorders such as anxiety or depression do not seem to influence the level of beta-carbolines.