In order to define the role of steroid injection and splinting as a method of treatment of carpal-tunnel syndrome, a prospective study was performed on fifty hands in forty-one consecutive patients. All hands were treated with a single injection and three weeks of splinting. Follow-up ranged from a minimum of six months to a maximum of twenty-six months, with a mean of eighteen months. All hands had characteristic symptoms of median-nerve compression at the wrist and increased distal median motor latencies. Eleven (22 percent) of fifty hands were completely free of symptoms at the end of the follow-up period. Hands that initially had mild symptoms and findings of less than one year's duration, normal sensibility, normal thenar strength and mass, and one to two-millisecond prolongations of either distal median motor or sensory latencies had the most satisfactory responses to injections and splinting. Hands with severe symptoms of more than one year's duration and findings of atrophy, weakness, and distal motor latencies of more than six milliseconds or absent sensory responses had the poorest response to injections and experienced a high rate of relapse.