The objective of this study was to investigate the epidemiology of toxoplasmosis in stray cats in Bangkok. Sera were collected during 2006 and examined by Sabin-Feldman dye test. Five hundred sixty-four male and 926 female cats in and around monasteries from 50 districts were collected. Toxoplasma gondii was detected in 72 (4.8%) of 1,490 cats. The prevalence was significantly higher in females (5.6%) than in males (3.6%). Cats more than 5 years old had the highest infection rate (5.1%). Fifty-six percent (28/50) of areas were positive for T. gondii in cats. Our results show T. gondii is widespread in stray cats in Bangkok. It is essential to control the number of stray cats in order to reduce the transmission of toxoplasmosis to animals and humans.