Between September 1983 and July 1985, a case-control study was performed of carpal tunnel syndrome risk factors in the general population of Maastricht, The Netherlands, and some surrounding villages. Twenty-eight of the 501 participants were found to suffer from carpal tunnel syndrome. These 28 were added to a series of 128 consecutive carpal tunnel syndrome patients from the same area. The 156 (131 women and 25 men) subjects in whom carpal tunnel syndrome had been diagnosed on the basis of clinical history and neurophysiologic testing were compared with the remaining 473 (310 women and 163 men) subjects. After adjustment for age and sex, the following carpal tunnel syndrome risk factors could be identified: activities with a flexed wrist or with an extended wrist (exposure-related increased risk), hysterectomy without oophorectomy, last menstrual period in menopausal women 6-12 months ago, height, weight, Quetelet index, slimming courses, and in men, varicosis. Associations between carpal tunnel syndrome and the use of oral contraceptives, age at menopause, diabetes, thyroid dysfunction, rheumatism, typing, and pinch grasp could not be demonstrated.