Objective: Symptoms such as anorexia and sleep disturbances are common and cause a significant reduction in quality of life in hemodialysis patients. Orexin-A, which is a neuropeptide produced in lateral hypothalamic neurons and involved in regulation of feeding behavior, energy metabolism and sleep-wake cycle, is a good candidate to play a role in sleep and feeding disturbances in these patients. The aim of this study was to investigate the relationship between orexin-A levels and anorexia and sleep disturbances in hemodialysis patients. Subjects and Methods: 70 hemodialysis patients and 70 age and sex matched healthy controls were compared according to their orexin-A levels. Plasma orexin-A levels were measured with the Enzyme Immunassay method. The Subjective Global Assessment Scale to assess nutritional status, and Pittsburg Sleep Quality Index to assess quality of sleep were used. Results: The mean orexin-A level of the patients was significantly lower than controls (p<0.001). Body mass index (r=-.313. p=0.01) and parathormone (r=-.341. p=0.006) were significantly correlated with orexin-A levels. After multivariate linear regression, the significance remained for body mass index (p=0.01) and triglyc-eride levels (p= 0.03). Conclusion: These preliminary results may suggest that plasma orexin-A levels can be used as a biochemical marker for assessment of the nutritional state in he-modialysis patients. 2010 © TurkJBiochem.com.