Thirty-one patients undergoing treatment with selegiline HCl for periodic limb movements in sleep (PLMS) were examined with respect to specific sleep composition in a retrospective study. Pre- and post-treatment overnight polysomnographs revealed a highly significant decrease in the number of PLMS per hour of total sleep time (P < 0.0005). The alerting effect associated with selegiline was not found to have significant effect on patients' sleep efficiency or sleep-onset latency (P > 0.10). As controversy continues regarding the medicated treatment of PLMS, our findings with selegiline point to an alternative for clinicians to consider.