Toxoplasmosis is a wide distributed opportunistic infection caused by Toxoplasma gondii. This was a cross-sectional study of T. gondii antibody titer, which was conducted from June 2003 to August 2004 on renal transplant recipients in Iran. A total of 551 serum samples were obtained from randomly selected population referred from different areas all over the country to Shafa Central Clinic in Tehran. Patient’s information was recorded in a questionnaire before sampling. Two samples of finger-prick blood were collected from each person and antibody titer against Toxoplasma was assessed by Indirect Fluorescence Antibody (IFA) technique on serum samples. Totally 39 cases (7.1%) of samples were positive for antibody by the titer of 1: 20 and higher. On investigation of risk factors, no significant difference was found between consumption of under-cooked meat, close contact with animals, and the source of drinking water and seropositivity rate of toxoplasmosis. The relatively low seroprevalence rate of Toxoplasma infection shows the successful approaches to awareness of transplant recipients about the potential risks of acquisition of infectious diseases due to regular administration of suppressive drugs. However, the regular surveillance through serological screening of Toxoplasma antibody in kidney transplant recipients is advisable