Immunodiagnostic tests for Taenia-specific faecal antigen based on polyclonal rabbit antisera against Taenia saginata or Taenia solium proglottid extracts in capture-type ELISA assays have been developed. Taenia-specific antigen was detected in detergent-solubilized faecal extracts from T. solium- and T. saginata-infected hosts. Coproantigen from T. solium-infected hamsters did not cross-react with faeces from rodents infected with Hymenolepis diminuta, H. citelli, H. microstoma, Necator americanus, Strongyloides ratti or Nematospiroides dubius and faeces from uninfected animals. When the T. saginata-capture ELISA was tested with faecal samples positive for T. solium antigen, no cross-reactions were obtained. However, faecal samples from humans infected with T. solium or T. saginata, including some with extremely low egg counts, were cross-reactive by either test. Nevertheless, considerably higher O.D. values were obtained with stool samples from Taenia patients compared to Hymenolepis nana-infected or uninfected individuals. Two individuals, infected with Taenia sp. and positive for coproantigens by ELISA, became antigen-negative 6 days after treatment with Niclosamide. The possibility of developing species-specific immunodiagnostic tests for human taeniasis through coproantigen detection is discussed.