Background Knowledge of how work demands vary between different practice areas could give us a better understanding of the factors that influence the working conditions in the health services, and could help identify specific work-related challenges and problems in the different practice areas. In turn, this may help politicians, and healthcare administrators and managers to develop healthy work units. The aim of this study was to find out how nurses' aides' perception of demands and control at work vary with the practice area in which the aides are working. Methods In 1999, 12 000 nurses' aides were drawn randomly from the member list of the Norwegian Union of Health – and Social Workers, and were mailed a questionnaire. 7478 (62.3 %) filled in the questionnaire. The sample of the present study comprised the 6485 nurses' aides who were not on leave. Respondents working in one practice area were compared with respondents not working in this area (all together). Because of multiple comparisons, 0.01 was chosen as statistical significance level. Results Total quantitative work demands were highest in somatic hospital departments, nursing homes, and community nurse units. Physical demands were highest in somatic hospital departments and nursing homes. Level of positive challenges was highest in hospital departments and community nurses units, and lowest in nursing homes and homes or apartment units for the aged. Exposure to role conflicts was most frequent in nursing homes, homes or apartment units for the aged, and community nurse units. Exposure to threats and violence was most frequent in psychiatric departments, nursing homes, and institutions for mentally handicapped. Control of work pace was highest in psychiatric departments and institutions for mentally handicapped, and was lowest in somatic hospital departments and nursing homes. Participation in decisions at work was highest in psychiatric departments and community nurse units, and was lowest in somatic hospital departments and nursing homes. Conclusion The demands and control experienced by Norwegian nurses' aides at work vary strongly with the practice area. Preventive workplace interventions should be tailored each area.