The authors study the influence of acute and chronic ethanol intoxication on the blood levels of rifampicin and isoniazid as well of aminoglycoside antibiotics in rats. While the acute ethanol intoxication has no influence on blood levels of tested antibiotics, in the chronic inotoxication lower levels of rifampicin and higher levels of isoniazid are observed. A study was performed also to determine the influence of an acute and chronic treatment with alcohol and the avoe quoted antibiotics on the BSP elimination rate. In the acute as well as in the chronic experiments, a constant significant delay in the elimination of BSP was observed in animals treated with rafampicin either alone or associated with alcohol. Isoniazid modified the dye elimination in comparison to controls only in chronic experiments. Ethanol did not seem to have any influence on this behavior. The implications and the possible significance of these findings are discussed.