The aim of this double-blind study was to compare the effect of high-dose (1000 mg) and low-dose (375 mg) methylprednisolone pulse therapy administered intravenously once daily for three consecutive days, in active ankylosing spondylitis. Seventeen patients with active ankylosing spondylitis were randomly allocated to high-dose (8 patients) or low-dose (9 patients) regimen. Although there was no placebo group in this study, it is our impression that in patients with active ankylosing spondylitis, both high-dose (1000 mg) and low-dose (375 mg) methylprednisolone pulse therapy given on three consecutive days, is effective as regards pain relief and improvement in spinal mobility. There were no statistically significant differences between the two groups, though there was a trend towards the high dose yielding a greater and longer lasting improvement. No serious adverse reactions were observed.