The extent of association between woodchuck hepatitis virus surface antigen and host hepatocyte plasma membrane in chronic hepatitis was studied. Purified membranes containing the antigen were treated with various agents which perturb plasma membrane constituents to elute woodchuck hepatitis virus surface antigen. The products from disrupted membranes were analyzed by sedimentation in sucrose gradients and tested to identify the antigen reactivity. The results indicated that membrane-bound woodchuck hepatitis virus surface antigen was partially released by 4 M potassium chloride, potassium thiocyanate and guanidine, 6 M urea or 0.1 N sodium hydroxide (pH 13.5), but not in the presence of low concentrations of these reagents or by 10% 2-mercaptoethanol and 1% sodium dodecyl sulfate. No more than 15% of the total membrane-associated woodchuck hepatitis virus surface antigen was eluted by 0.1 N NaOH, which was found to be the most effective eluent among tested agents at the antigen removal. The remaining woodchuck hepatitis virus surface antigen was resistant to further extraction with sodium hydroxide, as expected for an integral membrane protein. Treatment of the infected membranes with 1% Triton X-100 or 50 mM deoxycholic acid, that solubilize the membrane lipid bilayer releasing most of the integral membrane proteins, resulted in the sedimentation of almost all detectable woodchuck hepatitis virus surface antigen reactivity with the detergent-insoluble membrane residues, suggesting a firm interaction of the antigen with the plasma membrane matrix.(ABSTRACT TRUNCATED AT 250 WORDS)