Background: Steroids therapy remains controversial for the patients with stroke, but some physicians administrate it yet, in such a patient. For this reason, in a double-blind clinical trail, we evaluated the dexamethasone effects on the motor function of the patients with stroke.Materials and methods: In a double-blind clinical trail, and in contrast to placebo, eighty patients presented with hemiplagia and with the impression of stroke enrolled in two groups that received dexamethasone and placebo. In the first admission day, the patients evaluated for risk factors, muscle force, level of consciousness, sphincter and speech disorders. Muscle forces reevaluated for five days later. All the data extracted with a checklist and compared by descriptive statistics and x2, t test, Mann-Whitney, Friedman and repeated measure AN OVA tests.Results: Four patients excluded from the study for death. The age mean was 67.93±8.84 and 39 and 37 were male and female respectively. Except for sex and smoking, there was no difference in two groups. The muscle forces improved significantly in the patients in each groups (P value=0.000), but we didn't find any difference between them (P value=0.59). Also we didn't see any steroid complication.Conclusion: This study failed to demonstrate any benefit of dexamethasone in improving the motor function of stroke patients.