Chimpanzees infected with Schistosoma japonicum develop circulating schistosome antigens in their circulation between 6 and 9 weeks post-exposure. The minimum number of circulating antigens ranges from one to three. These antigens also cross-react with an antiserum against S. mansoni adult worms. Clearance of these antigens from the circulation several weeks later typically occurs. Persistence of these antigens could result in the observed renal damage.