Evaluation of stored iron by means of DFOX-induced sideruria in 101 subjects with various degree of hyposideraemia with or without anaemia, is reported. Three groups were examined: 49 patients with chronic loss of blood and malabsorption and urinary iron values up to 1 mg/24hr; 43 with non-bleeding neoplasia, collagen disease, lymphoma, cirrhosis of the liver etc. and values of 1-2mg/24 hr; 9 with rheumatoid arthritis and cirrhosis of the liver and values over 2 mg/24 hr. The reasons why hyposideraemia may accompany incipient of frank tissue hypo-, normo- or hypersiderosis are discussed.