In the introduction the authors summarize briefly knowledge on osteomalacia, its definition, causes, clinical picture, laboratory, X-ray, scintigraphic findings and treatment. They present the case-history of a patient with severe osteomalacia which was diagnosed and treated at the rheumatological department of the Thomayer Faculty Hospital. The assessment of the cause of osteomalacia in this patient is difficult.

        Key words: osteomalacia - D vitamin - calcitriol.