BACKGROUND: The activity of the immune system displays a circadian rhythm. In diseases characterised by aberrant immune activity, chronotherapy (a treatment regimen tailored to diurnal body rhythms) may increase the efficiency, safety and tolerability of drugs. AIM: To compare the outcomes of intravenous corticosteroid administration during the day or night, for treatment of acute multiple sclerosis relapses. METHODS: 17 patients with multiple sclerosis were included in the study. Clinical assessment of disability was performed at trial entry, and at days 7 and 30 from the initiation of treatment. Adverse events and preference of night-time versus daytime treatment were assessed at the end of the treatment course. RESULTS: After night-time treatment, clinical recovery was significantly (p<0.001) enhanced and the mean number of side effects was significantly (p = 0.007) lower. Furthermore, most patients expressed a preference for night-time versus daytime treatment. CONCLUSIONS: The study suggests a potential benefit for implementation of chronotherapy using steroid treatment for acute multiple sclerosis relapse, with implications for other immune-mediated disorders.