Selective deprivation of paradoxical sleep after learning results in memory deficits in a variety of tasks. The present experiment was designed to examine the effects of paradoxical sleep deprivation (PSD) upon spatial working and reference memory. Adult male Sprague-Dawley rats were trained for 10 days in an eight-arm radial maze. Food rewards were available in four of the arms, while the other four arms were never baited. After each daily training session, different groups of rats were given 4 h of PSD, beginning either immediately, 4 h, or 8 h after the training experience. An additional group received PSD during the period 13-24 h following daily training. The group that received PSD for 4 h immediately following daily training showed significant impairment compared to the other groups, but the deficit was limited to the reference component of the task. This result suggests that PSD causes deficits only in long-term forms of spatial memory.