Excretory/secretory antigens (ES) of larval Taenia solium were obtained by maintaining the bladder worms in Medium 199 for 3 days. Analysis by SDS-PAGE showed that ES antigens consisted of at least 19 polypeptides, with M(r) ranging from 14-116 kDa. Analytical isoelectric focusing revealed eight bands with acidic pI. An immunocytolocalization study using the peroxidase method demonstrated the presence of ES epitopes on the tegument of the wall of the spiral canals of bladder worms. The specificity of ES antigens was evaluated by EITB, ELISA and FAST-ELISA using antisera against the common parasites of Chinese pigs and man. ES antigens cross-reacted with the antiserum against larval T. hydatigena of pigs. However, these antigens were generally more specific in diagnosing human cysticercosis. Three host-like molecules with molecular masses 43, 58 and 66 kDa were present in the ES products.