This study is intended to find out whether treatment with rosiglitazone improves the state of the liver and related blood markers in patients with nonalcoholic steatohepatitis (NASH).

Phase one : A double blind randomized placebo controlled trial of rosiglitazone

• 64 pts with biopsy proven NASH will be randomized to receive either rosiglitazone 8 mg/day or placebo for one year.
• after one year of treatment patients will undergo a liver biopsy then a 4 month follow off treatment

Primary endpoint: improvement of at least 30% of the histological score of steatosis Secondary endpoints: improvement in ALT values, in necrosis and inflammation and fibrosis

Phase II extension open label trial

All participants to the phase one regardless of the drug received in the first year will be treated with rosiglitazone for 2 additional years. A liver biopsy will be performed at the end of these two additional years in order to find out whether prolonged rosiglitazone therapy further results in improvement of liver injury in NASH patients.

Inclusion Criteria:

• Histologically proven NASH with steatosis >= 20%
• Increased serum ALT

Exclusion Criteria:

• bland steatosis
• daily alcohol > 20/30 g (women/men)
• any other cause of liver disease
• secondary NASH including drug-induced steatohepatitis
• treatment with insulin or glitazones
• cardiac insufficiency
• Hb < 10 g/dl