On March 2, 1998, the National Public Health Network (RNSP) was notified by the health authorities of the Tarn-et-Garonne department of two outbreaks of trichinellosis that had occurred in February in that department. An epidemiological investigation was therefore launched on March 3 to assess the extent of the outbreak, identify the source and the food vehicle, and propose control measures. This article describes the alert procedure, the methodology used to identify the source of the outbreak, and the results of the epidemiological, parasitological, and veterinary investigations. (R.A.)