In order to determine the efficacy of the carpal compression test (CCT) in the diagnosis of the carpal tunnel syndrome (CTS), we conducted a prospective study on 200 consecutive hands diagnosed as having CTS. A control group of 100 healthy volunteers with no symptoms of CTS were also assessed. The results of the CCT in the patients and controls were compared with those obtained with Phalen's and Tinel's tests. CCT achieved a sensitivity of 87%, and a specificity of 95%. It is a simple, fast and very reliable provocative test, and should be routinely used in the diagnosis of CTS. This test is also an appropriate manoeuvre in wrists with limited range of motion or pain that cannot be assessed with Phalen's wrist flexion test.