Localised foot pain occurred in four patients with Paget's disease of bone or myositis ossificans who were treated with disodium etidronate (EHDP) in a dose of 10 to 20 mg/kg body weight/day for four to six months. There was localised tenderness and sometimes slight swelling at the painful areas. Bone x-rays were normal, but bone scans showed increased uptake of the isotope at these areas. The pain persisted for several weeks, causing considerable difficulty in walking. The symptoms were most likely due to diphosphonate-induced stress fractures. These cases emphasise the importance of administering EHDP in low dosage for short periods only.