We identified bilateral carpal tunnel syndrome in 19 of 43 living persons of a nonconsanguineous family. No single common etiologic feature was seen. Sixty-three percent of the afflicted kindred had symptomatic digital flexor tenosynovitis. Noninflammatory thickening of the flexor retinaculum or tendon sheaths, or both, was the commonest surgical finding. The 44% prevalence, early age of onset, and equal sex ratio differ from idiopathic carpal tunnel syndrome. Family pedigree suggests an inheritable disorder transmitted by an autosomal dominant gene with a high degree of penetrance.