On August 24, 1994, the National Institute for Occupational Safety and Health (NIOSH) received a request for a health hazard evaluation (HHE) from the International Association of Fire Fighters (IAFF) Local 2899. Local 2899 represents fire service personnel in the Anaheim Fire Department (AFD) in Anaheim, California. The request concerned psychologic changes and cardiac abnormalities possibly related to job stress from long work hours, night work, sleep deprivation, and other job stressors. On November 16, 1994, NIOSH investigators met with AFD and IAFF representatives to discuss the HHE request and to visit three fire stations. The meeting and visits were held for NIOSH investigators to learn about AFD work practices and work organization. On May 31, 1995, NIOSH representatives returned to Anaheim to obtain electrocardiogram (EKG) results from annual physical examinations and to carry out a health survey. NIOSH investigators conducted a questionnaire survey of full-time AFD employees. Participants filled out a questionnaire about personal characteristics, job history, medical history, cardiovascular symptoms, mental health (including depressive symptoms and anxiety), and job stress. For all study participants, NIOSH investigators obtained EKG results from the most recent annual physical examinations. A NIOSH occupational physician read the EKGs using standard clinical criteria. We did statistical modeling to learn whether job stressors were related to depressive symptoms, anxiety, and sinus arrhythmia. Two hundred ten (81%) of 260 full-time employees participated in the questionnaire survey. For this evaluation, we analyzed the data for the 196 participants who worked in one of the 10 fire stations. All but three participants were male, and the majority (75%) were in their 30s and 40s. Most participants were in one of the following four job titles: firefighter (66 persons, 34%), firefighter/paramedic (31 persons, 16%), fire engineer (31 persons, 16%), and fire captain (30 persons, 15%). On average, participants reported that depressive symptoms occurred "occasionally" during the past month. None of the participants reported having depressive symptoms "very often." Depressive symptoms were related to uncertainty about career, lack of support from co-workers, disharmony among co-workers, work effort, participation in fires with multiple burn victims, and years in the fire department. On average, participants reported that anxiety symptoms occurred "occasionally" during the past month. None of the participants reported having anxiety "very often." Anxiety was related to uncertainty about career, lack of support from co-workers, disharmony among co-workers, work effort, self-reported hazardous materials exposure, and participation in fires with multiple burn victims. EKGs were available for 179 of the 196 participants working in a fire station. The NIOSH physician reported that 73% (131 persons) were within normal limits and 27% (48 persons) were abnormal. The NIOSH physician noted several EKG abnormalities; the most common was sinus arrhythmia, occurring in 23 participants. The only other abnormalities noted in more than five participants were sinus bradycardia (11 persons) and conduction delay (10 persons). Due to the small number of participants with any single condition other than sinus arrhythmia, we focused further analysis on this finding. We did not find a meaningful linear relationship (that is, more job stress associated with more sinus arrhythmia) between sinus arrhythmia and any of the job stressors studied. Our evaluation found neither severe psychological problems nor a consistent pattern of clinically significant cardiac arrhythmias. We did, however, find evidence that certain aspects of the job affected the psychologic well-being of employees. These included the job stressors of uncertainty, disharmony, and work effort, and involvement in specific critical incidents, including fires with multiple burn victims and self-reported hazardous materials exposure. Recommendations are offered to ensure that Anaheim Fire Department personnel are receiving appropriate medical surveillance and to address concerns about job stress.