Using transmission electron microscopy and biochemical analysis, the effect of cuban red propolis against hepatitis induced by 1,000 mg kg-1 of galactosamine in rats was studied. An ethanolic extract of propolis was prepared and it was given to rats at doses of 10, 50 and 100 mg kg-1, 30 min before the hepatotoxin. Propolis extract prevented hepatocytes alterations induced by galactosamine. It was mainly seen in rough endoplasmic reticulum, Golgi complex, nucleus and plasma membrane of hepatocytes. Propolis extract induced reversion of the increased activity of alanine aminotransferase and malondialdehyde concentration in the serum of rats treated with galactosamine. The probable role of antioxidant activity of propolis in the prevention of hepatitis is discussed in this paper.