Vitamin D is a group of fat-soluble secosteroids, of which calcitriol is the most biologically active component. Research conducted in the last decade has indicated a role for vitamin D in pathogenesis of disorders of the central nervous system. The evidence for the role of vitamin D in multiple sclerosis, Parkinson’s disease, dementia, stroke, epilepsy, autism, schizophrenia and depression is discussed. This evidence is mainly based on studies that searched for an association between vitamin D blood levels or vitamin D intake and the incidence or the course of disease. Conclusions from clinical research on the value of vitamin D supplementation support the hypothesis of vitamin D involvement in multiple sclerosis. Data indicating a role of prenatal vitamin D deficiency in pathogenesis of schizophrenia and autism are referred to. The results obtained in animal models of vitamin D deficiency and molecular research on effects of vitamin D in pathogenesis of the aforementioned diseases are presented. They show that calcitriol is a neurosteroid that influences central nervous system development and regulates the activity of the immune system. Up-to-date information on vitamin D supplementation is included. The need for use of higher doses of calcitriol and the safety of doses of calcitriol up to 10 000 IU daily are highlighted.