We conducted a seroepidemiological survey of zoonotic parasite infection in inhabitants of East Java, Indonesia. The subjects of the survey were 244 persons selected from visitors to Sidoarjo City Hospital in East Java between May 1992 and October 1993. Ninety-seven had diarrhea and the rest came to the hospital for routine check-ups. All serum samples were tested for antibodies against five zoonotic parasites: Toxoplasma gondii, Entamoeba histolytica, Toxocara canis. Angiostrongylus cantonensis, and Anisakis species. Tests used were enzyme-linked immunosorbent assays (ELISA), latex agglutination (LA) test, indirect fluorescence antibody (IFA) test, hemagglutination (HA) test, and gel diffusion precipitation (GDP) test. Some 64% of the subjects had antibodies to T. gondii. The prevalence of antibodies to E. histolytica varied from 2 to 15% depending on the test, but the true rate was probably the 7% or 8% obtained by the HA and IFA tests. The proportions of subjects with positive results were 63% for T. canis, 17% for A. cantonensis, and 11% for the Anisakis spp. The prevalence of antibodies to T. gondii and T. canis was lower in subjects aged 1 to 9 years than in older subjects, probably because the persons in this group had less time to be infected. Antibody titers to A. cantonensis and the Anisakis spp. were high in the juvenile group, perhaps because recent changes in eating habits have increased opportunities for infection.