1,2-Dibromo-3-chloropropane (DBCP) induced DNA damage, measured by alkaline elution, at low concentrations (5-10 microM) in suspensions of hepatocytes and testicular cells isolated from rats. At higher concentrations (greater than or equal to 100 microM) DBCP caused DNA damage and increased the frequency of sister chromatid exchanges in Chinese hamster V79 cells. When DBCP (2.5-10 microM) was tested for its ability to cause unscheduled DNA synthesis (UDS) in monolayers of liver cells isolated from untreated rats, a clear positive response was obtained. No increase in UDS was detectable when liver cells isolated from PCB-pretreated rats were used. In contrast, DBCP (greater than or equal to 50 microM) was metabolized in hepatocytes from PCB-pretreated rats to products mutagenic to Salmonella typhimurium TA100 in co-culture with the hepatocytes, whereas control hepatocytes were substantially (40-fold) less active. No bacterial mutagenicity could be detected when the TA100 strain was co-incubated with isolated rat testicular cells and DBCP. In co-cultures of hepatocytes and V79 cells DBCP-induced DNA damage in V79 cells occurred at low concentrations (10 microM DBCP) compared to the concentration (100 microM) needed to induce DNA damage in the V79 cells incubated without hepatocytes. Testicular cells were not able to enhance DBCP-induced DNA damage in the V79 cells. The data indicate that the putative reactive DBCP episulphonium ion metabolite formed in the testicular cells presumably responsible for testicular cell DNA damage, is not capable of escaping the cell where it is formed. Other reactive DBCP metabolites generated in the liver cells seem to be able to interact with the DNA of neighbouring cells.