OBJECTIVE: The aim of this study was to assess the association between work hours and incidence of hypertension in 8779 participants of a Spanish dynamic prospective cohort of university graduates. METHODS: The baseline questionnaire included information about the weekly number of hours the participants devoted to work and to home chores. The work hours were grouped into four categories: 39 or less, 40-49, 50-59, and at least 60 for men; 29 or less, 30-39, 40-49, and at least 50 for women. We added up the number of hours working and spent in home chores in what we called 'total activity hours' that was categorized in quartiles, specific by sex. A participant was classified as an incident case of hypertension if he/she was initially free of hypertension at baseline and reported a physician-made diagnosis of hypertension in at least one of the follow-up questionnaires. The associations between work hours or 'total activity hours' and incidence of hypertension were estimated by calculating the multivariable-adjusted odds ratio and its 95% confidence interval, using logistic regression models. RESULTS: The cumulative incidence of hypertension during 4.2 years median follow-up was 5.8%. No association was found between work hours or 'total activity hours' and incidence of hypertension in either sex. CONCLUSION: The results of our study do not support any association between work hours and incidence of hypertension. Further longitudinal studies in the general population should be conducted to test this relationship.