The purpose of this study was to investigate the effects of PPAR alpha agonist on metabolic parameters in naturally Fasciola-infected sheep. Twenty sheep with fasciolosis were allotted in 2 equal groups according to the received treatment (triclabendazole/levamisole in the group I and triclabendazole/levamisole + PPAR alpha agonist (2-methyl-2-phenoxy-propionic acid) in the group II) and the haematological and biochemical parameters were assessed before the treatment and 7, 14 and 28 days after and were compared to control values determined from 10 healthy sheep. As expected, fasciolosis has induced an anaemia evidenced by low haematocrit and low haemoglobinemia coupled to eosinophilia and to a moderate lymphopenia, severe liver damage characterised by hepatocyte degenerescence (significant increases in serum AST and GDH activities) and bile duct obstruction (significant increases in serum GGT activity and in serum bile acid concentrations) leading to impairement in liver metabolic functions (hypoalbuminemia, marked decreases in serum glucose concentrations and in LDL associated cholesterol concentrations). All the heamatological and biochemical alterations were at least partially alleviated by the antihelminthic treatment except the serum triglyceride concentrations which have continued to decrease during the post-treatment period and the total cholesterol and HDL associated cholesterol concentrations which have markedly increased, particularly when sheep were also treated with the PPAR alpha agonist. These results clearly demonstrated the severe metabolic liver impairment occurring during fasciolosis in sheep and the beneficial effects of the PPAR alpha agonist on the correction of the negative energy balance, particularly by promoting the reverse cholesterol transport.