Two U.S. surveys suggested that dental hygienists (DHs) may suffer from carpal tunnel syndrome (CTS), but these studies did not use validated questionnaires, adjust for confounders, or include external controls. We conducted a questionnaire survey of all 2,142 DHs belonging to the Ontario Dental Hygienists' Association, and a referent group of 305 dental assistants (DAs), who do not scale teeth. The Standardized Nordic Questionnaire was used as the basis for asking about musculoskeletal symptoms. The response rates in the two groups were identical. Of the DHs, 7.0% had been told by a physician since starting work that they had CTS, but only 1 of 65 had received workers' compensation. Compared to the DAs, after adjusting for age the DHs were 5.2 times (95% confidence interval [CI] 0.9-32) more likely to have been told they had CTS and 3.7 times (95% CI 1.1-11.9) more likely to meet a CTS case definition. The DHs were also 2.5 (95% CI 1.6-3.9), 2.8 (95% CI 1.8-4.4), and 1.8 (95% CI 1.2-2.7) times more likely to report hand/wrist, shoulder, and neck problems in the past 12 months, respectively, but were less likely to report low back trouble. In internal analyses among DHs using logistic regression models, the number of heavy calculus patients per day, "clock" position around the dental chair, and years in practice were significant predictors of CTS. Days worked per week (but not heavy calculus patients), time with the trunk rotated, and years of practice were significant predictors of reported shoulder trouble in the past 12 months. Given that there are more than 9,000 DHs in Canada and about 100,000 in the United States, these findings suggest an important public health problem. They highlight the need to inform DHs during training and continuing education about musculoskeletal problems in general and CTS in particular. Attention should be directed to areas such as work station design, posture, treating patients with heavy calculus, and scheduling rest periods.