The effect of carpal tunnel area on the risk of carpal tunnel syndrome (CTS) was examined in this study. The subjects consisted of 27 workers diagnosed with CTS and 34 asymptomatic controls. All subjects were examined by a neurologist to verify case status. The controls were matched to the CTS cases for sex and age. The subjects completed a questionnaire concerning medical history. Computerized axial tomography (CT) was used to evaluate the carpal canal area of both wrists. In addition, nerve conduction velocity (NCV) studies were conducted to determine median nerve function. The carpal canal areas of both the right and left wrists were consistently and significantly larger in the CTS cases than in the controls. Females exhibited significantly smaller carpal canal areas than males. For all subjects combined, the distal CT measurement was significantly smaller than either the proximal or median CT measurements. Regardless of sex or hand, the carpal canal area had a cone like shape. All subsequent analyses were based on the smallest CT measurement of carpal canal area. The subjects were reclassified into case and control groups based on the results of NCV studies. In this way, seven asymptomatic subjects who nonetheless displayed decrements in NCV were reassigned to the case group. According to the new classifications, the carpal canal area was significantly larger in CTS cases than in controls. Analyses were also conducted with these seven asymptomatic subjects excluded. Once again, carpal tunnel area was significantly larger in CTS cases than in controls. The authors conclude that a small carpal tunnel area is apparently not a risk factor for CTS.