The nature of sleep is one of the major sources of dissatisfaction with the quality of life among patients with Parkinson's disease (PD). Difficult sleep maintenance (light and fragmented sleep) and difficulties with sleep initiation are the earliest and most frequent sleep disorders observed in these patients. Sleep disorders are also common in the normal elderly population, suggesting that normal aging may play a role in the etiology of sleep disorders in PD. Factor et al. examined the frequency of various sleep disorders in PD and compared them to those of normal elderly subjects. Sleep fragmentation and spontaneous daytime dozing occurred much more frequently in PD patients than in controls. Sleep fragmentation in PD may be due to an increased skeletal muscle activity, disturbed breathing and REM/non-REM variations of the dopaminergic receptor sensitivity. In parkinsonian patients who developed motor fluctuations (on-off phenomenon, wearing-off) during the day, other common sleep-related motor complaints including nocturnal akinesia, dystonia and painful cramps are observed. In a double-blind cross-over study, we compared the efficacy of a single dose of a chronic release formulation of levodopa/carbidopa (Sinemet CR) with that of a placebo in improving sleep-related motor disturbances in a group of 40 fluctuating PD patients. Sinemet CR significantly improved nocturnal akinesia and increased the hours of sleep in this group of patients. Initiation and maintenance of sleep are problems that may not be solved with antiparkinsonian treatment.