AIM: To clone and analyze the cDNA encoding immunodiagnostic antigen of cysticercosis. METHODS: Immunodiagnostic antigens of cysticercosis were obtained studied using recombinant DNA techniques. cDNA was synthesized from mRNA and a λgt11 expression library was constructed and immunoscreened with human and/or pig cysticercosis sera. RESULTS: Four positive cDNA clones (λcC1、λcC2、λcH1 and λcP1) were isolated. The λcC1 cDNA was 1 070 bp in length and consisted of a single open reading frame. The open reading frame of 747 bp encoded a polypeptide of 249 amino acids with a molecular weight of 27.36 kDa. The λcC1 fusion protein was identified as an common antigen for immunodiagnosis of both human and pig cysticercosis. CONCLUSION: The λcC1 fusion protein was highly sensitive and specific as compared to crude somatic antigen for the immunodiagnosis of cysticercosis.