The enzyme-linked immunosorbent assay (ELISA) was used for the serodiagnosis of four parasitic infections. ELISA was performed as a macromethod in polystyrene tubes and/or as a micromethod in polystyrene microplates. Conventionally raised pigs were infected orally with different numbers of Trichinella spiralis larvae, and the pigs' sera were tested for antibody to T. spiralis. Results were compared with those from sera of uninfected conventionally raised pigs. Cynomolgus monkeys were infected orally and immunized with Toxocara canis. The results of macro-ELISA and micro-ELISA were compared with those of immunofluorescence. Micro-ELISA proved to be more sensitive than macro-ELISA, the latter being more sensitive than immunofluorescence. The applicability of ELISA for seroepidemiology was demonstrated by results obtained with sera from patients with proved African trypanosomiasis. With both macro-ELISA and micro-ELISA it was possible to discriminate between the positive and negative sera. ELISA was used for study of the seroepidemiology of toxoplasmosis. Again, positive sera could be distinguished from negative sera. The examples presented show that ELISA can be used as an additional serologic tool for the detection of both helminthic and protozoal infections.