Background: Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system resulting from demyelination and axonal loss. Although treatment of MS has progressed, patients continue to have attacks and treatment for such episodes remains a subject of ongoing study. The object of this study is to determine the effect of intravenous methylprednisolone (IVMP) on the degree of DISABILITY in MS patients.Methods: This cross-sectional study involved 63 patients with a definite diagnosis of MS, based on the MacDonald criteria, at the Iranian Center for Neurological Research at Imam Khomeini Hospital, Tehran, Iran, from March 2004 through March 2005. After obtaining informed consent, investigators gathered data including each patient's age, gender, pyramidal activity STATUS, cortical, cerebellar and brain stem activity STATUS, sensory signals in the extremities, including vibration, touch, pain, position, visual STATUS, as well as bladder and intestinal activity, and EXPANDED DISABILITY STATUS SCALE (EDSS) score. SPSS version 11 was used for data analysis.Results: A five-day regimen of IVMP (5g) significantly reduced the immediate posttreatment score from 4.595 to 3.635, which represents a 96% improvement in the EDSS. The greatest change in functional system DISABILITY was seen in the pyramidal system with a mean score of 1.13. After treatment, the rate of DISABILITY reduction in the sensory system, cerebellum, vision, bladder and intestinal activity was 0.57, 0.49, 0.46, 0.4, and 0.38, respectively. Patients who had experienced fewer relapses responded better to treatment. There was no statistically significant relationship between patient age and the level of response to treatment. However, the rate of DISABILITY reduction after treatment was greater in males than females (p=0.05).Conclusion: These results show that IVMP treatment induces an immediate posttreatment effect that could partly account for clinical and radiological improvement in MS patients. However, further study is required to determine the possible long-term, or even intermediate-term, effects of methylprednisolone treatment on the course of this disease.