Epidemiological investigations on Fasciola hepatica fasciolasis were carried out from July 2004 to June 2005 in the Gafsa oases (Tunisia) after the detection of a human case. Three habitats were studied: one in El Gsar and two in Ain Soltan. The prevalence of human infection was 6.6%. The presence of the parasite was detected through serology in 14.3% of cattle, 35% of sheep and 68.4% of goats. The plants Apium nodiflorum, Oxalis cernua and Sonchus maritimus were suspected to be at the origin of animal contamination and Apium nodiflorum was incriminated in human infection. The prevalence of the infection of the intermediate host Galba truncatula (G. truncatula) was 19.2% from July 2004 to June 2005. Gafsa oases constitute a new location for the development of fasciolasis in the southern west of Tunisia.