From an investigation extending over the past 10 years and consisting of 20 extremities with median nerve compression associated with Colles' fracture in 19 patients, the authors make the following observations: (1) The carpal tunnel syndrome is frequently associated with a Colles fracture. (2) Median nerve compression often occurs after immobilization with wrist in Cotton-Loder position. Consequently, this position should rarely, if ever, be used in treatment. (3) Surgical decompression of the median nerve, by releasing the transverse carpal ligament, is indicated when pain and loss of sensation are severe. (4) Nonoperative treatment to control edema, including injection of hydrocortisone into the carpal tunnel, is usually adequate in milder cases. (5) Factors associated with the carpal tunnel syndrome that follows a Colles fracture may be classified as primary (median nerve caught between fractured ends of radius) and delayed (edema, position of hand during immobilization, and tenosynovitis).