The aim of this study was to assess the effect induced by the dopamine agonist dihydroergocristine (DHEC, CAS 17479-19-5), whose memory-improving activity is well-known, on sleep pattern and cognitive function, and the possible relationship between them. Ten elderly volunteers were included in the study. Selected subjects had to be neither demented nor depressed, according to neuropsychodiagnostic criteria (SCAG < 30, Hachinski dementia score < or = 15, Hachinski ischemic score < 6, HRSD < or = 22). All subjects underwent a nightly polysomnographic evaluation during placebo, after single and long-term once-daily 6 mg DHEC administration. Cognitive function and attention were also assessed by the Randt memory test and WAIS digit-symbol subtest. DHEC caused a marked and significant increase in the acquisition subitem, and memory improvement was documented during DHEC treatment. A significant direct relationship between the effect of DHEC on REM sleep and memory test was also evidenced. Our results confirmed the role of REM sleep in the restoration of cognitive function.