An in vitro approach for studying human tissue metabolism and mutagenic activation of chemical carcinogens have been developed. Freshly isolated, intact cells from humans as well as rodents are used for metabolic activation. Reversion of S. typhimurium is used to assess biological activity of metabolites and HPLC analysis of metabolites have been conducted. Work during the past year has centered on developing a system for frequent human tissue acquisition. A human system has been developed to investigate differences between individual humans and differences between human and rodent liver, kidney and colon cell activation/ metabolism of aromatic amines. Metabolism, mutagenic activation and inter-individual variation has been measured and significant differences found betwen individual humans for these tissues. Comparisons of these human tissues to the respective rodent tissues are in progress.