Although Toxoplasma gondii infection generally shows subclinical courses in adults, it may have severe pathologic effects on the fetus. For a survey of toxoplasmosis in Shahr-e-Rey area, south of Tehran, Iran, we conducted a serological study on 1,187 general populations using indirect fluorescent antibody (IFA) test. In this cross sectional study, cases were selected randomly by a local primary health care (PHC) system. Blood samples were collected in microcapillary tubes and sera were examined by IFA after centrifugation. It has been shown that 68.3% of cases in all age groups had IFA titer of 1:10 and higher, which we consider as positive cases, and the rate for 1:400 or over was 30.2%. There was meaningful correlation between anti-Toxoplasma antibody titers and age, sex, and occupation of subjected people (P < 0.05%). The incidence was higher in females and highest in the children age group (10-14 years old). The present study demonstrates high prevalence of Toxoplasma infection among the people in south of Tehran, Iran.