In legal medicine, it is an established procedure to determine blood levels of ethanol in the living body or the corpse and estimate the level of drinking after establishment of the fact of drinking. In this process, effects of external factors, such as differences in the individual bodies, physical condition, various diseases, impact of food or drugs, exercise and bathing, present a problem. This paper describes a study on changes in blood levels of ethanol and its metabolites under the influence of varied factors as viewed from the practice of legal medicine. When rabbits were orally given Japanese "sake", there was a positive relationship between the dose of ethanol and its levels in the blood, whereas there was no such relationship with acetaldehyde or acetate. In the forced walk experiment in rabbits, no changes could be found in the levels of ethanol or acetate, but high levels of acetaldehyde were found in some animals. When the animals were bathed in hot water, acetaldehyde disappeared in the blood rather quickly in some rabbits, but the blood levels of acetate remained unchanged. Concurrent administration of sugar and Japanese "sake" to the experimental animals tended to acelerate metabolism both of acetaldehyde and acetate as well as ethanol. Administration of cyanamide elevated the acetaldehyde levels, and similar effect occurred with ethanol and acetaldehyde levels, in rabbit with a CCl(4)-damaged liver. In rabbits given ethanol every other day for 10 months, normal function was maintained in the liver, and high blood levels of ethanol were found in some animals. On the other hand, no significant changes occurred in acetaldehyde or acetate levels.