In a prospective double-blind study, we compared dexamethasone and placebo in 33 subjects with lumbosacral radicular pain. Of subjects with resting pain, 7/21 improved on dexamethasone, and 4/12 improved on placebo. Of subjects with pain on straight-leg raising, 8/19 improved on dexamethasone and 1/6 on placebo. Of 27 subjects evaluated 1 to 4 years after treatment, 8/16 who had received dexamethasone were asymptomatic or had only occasional mild low-back pain, compared with 7/11 who had received placebo. Thus, dexamethasone is not superior to placebo for either early or long-term relief of lumbosacral radicular pain, but may reduce pain evoked by stretch of acutely inflamed spinal nerve roots.