The most common cause avascular osteonecrosis (AVN) is corticosteroid medication. However, the impact of pulse steroid therapy on AVN development is not known properly. We intended to investigate the effect of this therapy on AVN development in multiple sclerosis (MS) patients. MS patients without AVN, chronic alcoholism, thrombophilia, sickle cell anemia, inflammatory bowel disease, cytotoxic drug usage history participated in the study. All of the patients were ambulatory (EDSS < 4). Thirty-three MS patients who received pulse steroid therapy at least 10 g or at least 15 g during the course of the whole disease, were the treatment group and 27 MS patients who did not receive any steroid therapy were the control group. There was no statistical difference between groups for age, sex and disease duration. Bilateral femoral magnetic resonance imaging (MRI) was performed to the both groups. In the treatment group, five patients (15.5%) had AVN whilst no AVN was found in the control group. In conclusion, it is interesting to find AVN at such a high rate in the MS patients who received pulse steroid therapy without any AVN history or complaint. The neurologists have to be more careful about AVN which early diagnosis is important to prevent the complications.