The aim of this study was to evaluate and analyze the incidence and features of headaches in patients undergoing hemodialysis. In this prospective study 318 patients, 119 women and 199 men, undergoing chronic HD in four hemodialysis centers in Serbia, were questioned about their problems with headaches using a questionary designed according to the diagnostic criteria of the International Headache Classification of Headache Disorders (ICHD) from 2004. Patients were distributed in two groups according to the presence of hemodialysis headaches (HDH). The groups were compared regarding sex, age, duration of HD, primary diseases that lead to ESRD, arterial systolic and diastolic blood pressure (BP) and serum levels of hemoglobin, urea nitrogen, creatinine, sodium, potassium, calcium, phosphates, albumin, glucose and calcium-phosphate product. We also analyzed features of HDH. The results were statistically compared. Patients with HDH had significantly lower serum glucose, but higher serum phosphates and albumin than patients without headaches. Furthermore, HDH patients had higher calcium phosphate product and systolic blood pressure than non-HDH patients. Out of 318 patients included in the study, 21 (6.6%) patients had HDH. According to our results, HDH appeared more frequently in men, during the 3rd hour of HD in more than a half of the patients and lasted less then 4 h in the majority of HDH patients. In the majority of patients HDH was bilateral, non-pulsating, without associated symptoms and it appeared mostly during HD. Personal history was negative for primary headaches in all patients with HDH. We believe that the results of our investigation of more than 300 HD patients pointed to some biochemical changes, possibly implicated by pathophysiology of HDH and disclose some specific HDH features that might contribute to a better understanding of this secondary headache disorder.