Membrane changes of DAB hepatic carcinoma cells were examined immunohistochemically, using the binding activity of Arachis hypogaea agglutinin (PNA) and anti-liver membrane antibody (anti-LM) from patients with HBsAg-negative chronic active hepatitis. The hepatic carcinoma in rats was produced through DAB feedings for 3-5 months. As controls, non-cancerous liver tissues from rats fed DAB, and normal rat liver were used. In isolated calls of the hepatic carcinoma and control tissues, FITC-PNA binded in 10 of 11 cases of DAB hepatic carcinoma and in none of control cases (11 rats fed DAB and 2 normal rats). In tissue sections, similar results were obtained. Lens culnaris agglutinin did not show any difference in binding among the 3 groups. Two anti-LMs did not bind to the membranes of isolated calls in 3 of 10 DAB hepatic carcinomas, although the anti-LMs were bound in all of controls. These facts indicate that the transformation, DAB hepatic carcinoma cells is accompanied by changes in the cell membrane, and that PNA may be useful in the analysis of membrane changes in carcinogenesis.