Surface-bound alpha-fetoprotein (AFP) was demonstrated by immunofluorescence on approximately 1/3 of splenic lymphocytes in chronic murine graft vs. host (GVH) reactions. Splenic lymphocytes were also shown to have a suppressed phytohemagglutinin (PHA) response compared to controls while lymph node cells from the same GVH animals revealed no surface AFP and had normal PHA responses. Splenic lymphocytes showed marked synthesis of AFP in the GVH and mixed lymphocyte culture (MLC) reactions by [14C]leucine incorporation and by radioimmunoassay in MLC supernates. Lymph node cells, however, demonstrated less synthetic activity and 14C counts in their membrane fractions were not markedly elevated.