SummaryThe paper reports pancytopaenia induced by Triamterene in a patient with idiopathic haemochromatosis. Some aspects of the antifolate activity of Triamterene and folate metabolism in haemochromatosis are discussed.Severe haematological disturbances related to Triamterene administration in alcoholic cirrhosis have been reported (3–5). We describe a case of Triamterene-induced pancytopaenia in a patient with idiopathic haemochromatosis and folic acid deficiency.