Experiments were performed to assess the role of liver cell necrosis in the induction of early steps in liver carcinogenesis with diethylnitrosamine, as measured by the appearance of foci of resistant hepatocytes that stain for .gamma.-glutamyl transpeptidase and that are presumptive preneoplastic lesions in the rat. With the use of a necrogenic dose of diethylnitrosamine and an assay for the carcinogen-induced early stages or resistant hepatocytes, the number of enzyme-altered foci was decreased to a major extent (up to 62%) by posttreatment with diethyldithiocarbamate, a derivative of disulfiram. Such posttreatment decreased to a large degree (78%) the cumulative labeling index of hepatocytes following an initial exposure to diethylnitrosamine. The performance of partial hepatectomy up to 68 h after such posttreatment restored the level of the induction of the resistant hepatocytes. Nonnecrogenic doses of diethylnitrosamine or dimethylnitrosamine induced virtually no foci of resistant hepatocytes but did so when coupled with cell proliferation. An important role for liver cell necrosis was established in the production of early steps in liver carcinogenesis in one model. The mechanism for this effect appears to be by the induction of compensatory liver cell proliferation.