OBJECTIVE: This study adapted ecological momentary assessment methods to: (a) examine differences in work stress between nurses and physicians, and (b) to study relationships between work stress, work activity patterns, and sleep. DESIGN: A total of 185 physicians and 119 nurses (206 women, 98 men) working in four teaching hospitals participated in an observational study of work stress. MAIN OUTCOME MEASURES: Participants carried handheld computers that randomly prompted them for work activity, patient load, and work stress information. RESULTS: Participants completed more than 9,500 random interval surveys during the study (an average of 30.8 surveys per person-week). Approximately 85% of all surveys were completed in full (73.3%) or partially (11.6%). Emotional stress scores among physicians were nearly 50% higher (26.9[19.0]) than those of nurses (18.1[14.9], r[302] = .37, p < .001). Direct and indirect care activities were associated with higher stress reports by both clinician groups (rs[159] = .14-.26, ps < .01). Sleep quality and quantity were predictors of work stress scores (ps < .05). Finally, higher work stress and lower sleep quality were also associated with poorer memory performance (r[302] = -.12, .17, ps < 05). CONCLUSIONS: The findings identify patterns of work stress in relationship to work activities, sleep habits, and provider differences that may be used to assist ongoing hospital work reform efforts. (c) 2009 APA, all rights reserved