This paper reports the results of a survey of 1000 certified dental assistants in Ontario, Canada. The aim was to obtain data on work-related stress, its sources and predictors. Of those responding to the survey, 38.8% said that their work was moderately stressful and 14.5% said it was very or extremely stressful. Approximately one-third had been bothered by stress at work on three or more days in the previous week. The main sources of stress were working under constant time pressures, running behind schedule and feeling undervalued by the dentist. Stepwise regression analysis revealed that the main predictors of work stress were not having a clear job description, working long hours, life stress while not at work and age. However, these variables explained less than 10% of the variance in job stress scores. Overall, 22.8% said it was very likely that they would seek work in another practice or seek work outside dentistry in the coming year. There was a significant association between work stress and job intentions; 43.0% of those reporting high levels of stress intended to change jobs compared to 8.9% of those who said that their job was not at all stressful (P less than 0.0001). These findings have implications for the way in which dental practice is organised and managed.