In October 2004, a swine farm in Jinchang, Gansu Province, China, experienced an outbreak of toxoplasmosis. Most of the affected pigs had a rectal temperature greater than 40 degrees C and gradually lost their appetite. Morbidity reached 57%, and mortality was approximately 2%. Analysis of blood samples from affected pigs using hemagglutination inhibition (HI) assay, immunoglobulin G-enzyme-linked immunosorbent assay (IgG-ELISA), and IgM-ELISA tests showed high titers of anti-Toxoplasma gondii antibody. Tachyzoites of T. gondii were found in body fluids of mice inoculated intraperitoneally with ground samples from the heart, liver, spleen, and brain of 2 sick pigs. In addition, the inoculation of 5 pigs with T. gondii tachyzoites caused death in 2 of the pigs. The origin of this outbreak was concluded to be food-borne T. gondii infection.