Previous investigations have shown that REM sleep deprived (REM SD) rats display an enhanced response to dopamine agonists. This action seems to be mediated through a supersensitivity of dopamine post-synaptic receptors. Accordingly, REM SD was performed on rats with an experimental model of Parkinson's disease. The animals were bilaterally lesioned in the nigrostriatal pathway through a stereotaxically directed electrical current. Seven days after the surgery the animals were REM SD for 72 hours and immediatelly after the end of this period were observed in an open field for ambulation, rearing, grooming, and latency. In comparison with non-deprived rats there was a significant increase in ambulation and rearing, a response that appeared again after a second REM SD period on day 21th after the surgery. These data of improvement of two parameters of an experimental model of Parkinson's disease suggest that SD may be useful in this condition.