The activities of cytosol superoxide dismutase (CuZnSOD) and mitochondrial superoxide dismutase (MnSOD) were measured in subcellular fractions of homogenates prepared from the brain, thymus and liver of ovariectomized (OVX) female rats, non-treated or treated 24 h prior to sacrifice with a single s.c. dose of 0.1 ml olive oil. In the brain, neither MnSOD nor CuZnSOD were affected by olive oil, whereas in the thymus the olive oil injection elevated CuZnSOD and did not affect MnSOD activity. At the same time, the activity of CuZnSOD was reduced and that of MnSOD was elevated in the liver following oil treatment. These results suggest that olive oil has modulatory effects on the expression of CuZnSOD and MnSOD activity in the liver and of CuZnSOD in the thymus of female rats.