The effects of the oxygen radical generating system hypoxanthine (HX)/xanthine oxidase (XO) on the [3 H]--dopamine uptake, the TBARS- and thiol content in striatal synaptosomes of adult rats were examined. Preincubation of synaptosomes with 20 mU XO/0.25 mM HX diminished the dopamine uptake and oxidized thiol groups of synaptosomes. Under these conditions no increase of TBARS, an indicator of lipid peroxidation, was observed. We concluded that in the used hypoxia model free radical mediated damage does not occur.