The population-genetic aspect of the investigation of acetylation is associated with the use of sulfadimezin (I) as a model preparation for the determination of the acetylator phenotype [i]. In this case the quantitative characteristic permitting an individual to be assigned to one acetylator or another ("fast" or "slow") is A-the ratio of the acetylsulfadimezin (II) concentration to the concentration of the "total" preparation (II + I) in the urine and (or) blood collected at a definite point of time. Such typing is based on the existence of genetic polymorphism of the acetylation os a number ol xenobiotics, which finds expression in the bimodality of the distribution of the values of A. Since population studies associated with the determination of the acetyiator status have been conducted with the so-called adult contingent, it is of interest to evaluate the nature of the distribution of the acetylator phenotypes in concrete age groups. The present work is devoted to an investigation of a sample of elderly individuals in this aspect.