Osteonecrosis of the femoral head is a severe complication of corticosteroids, which may lead to more disability in multiple sclerosis (MS) patients because of delayed diagnosis. The exact dose and risk period of steroids which cause the necrosis are not clearly known. The aim of the study was to enhance the attention of clinicians to leg pain in MS patients with regard to steroid therapies. We report five MS patients with femoral head necrosis who had relapsing remitting MS and received different doses of methyl prednisolone. Our young cases consist of three females and two males. The duration of disease varied between 1 and 3 years. The least interval between the last pulse of prednisolone and diagnosis of avascular necrosis was 6 months. Two of them received one pulse of 5 g of methyl prednisolone. All five patients had delayed diagnosis because the signs and symptoms were attributed to MS, which indicate the necessity of further focusing attention to early evaluations.