The role of disturbances of the iron metabolism (DIM) in idiopathic sudden hearing loss (ISHL) was investigated in 426 patients with ISHL who received iron therapy, anti-DIM medication, vitamins, and a combined regimen in a randomized study which was stratified by stages and groups. Low concentrations of haemoglobin, serum iron, serum ferritin, and red cell basic ferritin as well as abnormal circadian variations in the serum iron level were observed. The results were significantly better in patients receiving iron therapy than in those receiving anti-DIM medication, vitamins, and the combined regimen. Hearing improvement was achieved in 53.26% of the patients whose treatment started later than 3 months after the onset of the disease. The clinical association of DIM and ISHL is discussed.