OBJECTIVE: To assess factors associated with professional and total hours of work (work + home) among nursing staff. METHODS: Cross-sectional study conducted in a university hospital in the city of São Paulo, southeastern Brazil, between 2004 and 2005. A total of 696 workers (nurses, nurse technicians and aids), mostly women (87.8%) working day and/or night shifts, participated in the study. A selfadministered questionnaire was used to collected information on demographic characteristics, and working and life conditions. Translated and adapted into Portuguese versions of the Job Stress Scale, Effort-reward imbalance, ShortForm-Health-related quality of life and the Work Ability Index were also administered. Logistic regression models were used for data analysis. RESULTS: Sole breadwinner, working night shifts and effort-reward imbalance were the variables associated with both professional (OR = 3.38, OR = 10.43, OR = 2.07, respectively) and total hours of work (OR = 1.57, OR = 3.37, OR = 2.75, respectively). There was no signifi cant association between the variables related to hours of work and low Work Ability Index. Inadequate rest at home was statistically associated with professional (OR = 2.47) and total hours of work (OR = 1.48). Inadequate leisure time was signifi cantly associated with professional hours of work (OR = 1.58) and barely associated with total hours of work (OR = 1.43). CONCLUSIONS: The sole breadwinner, working night shifts and effortreward imbalance are variables that need to be further investigated in studies on work hours among nursing staff. These studies should explore workers’ income and the relationship between effort and reward, taking into consideration gender issues.