Objective: The service type offered by a home care agency contracted by the Queensland government is not based on the qualifications of the worker providing the service, but the service itself. This allows agencies to substitute certain levels and categories of labour in order to provide a service to meet their contract obligations. This study investigated evidence of labour substitution between nursing and allied health services. Method: Correlation and regression analysis was performed on the data collected from 218 clients of a branch of a community-based service agency operating nationally in Brisbane, Australia, during April, May and June 2005. Results: The results of the regression analysis revealed that when either allied health or nursing time rose by 10%, all else held constant, it was predicted that the other would fall by 4%. The subcategories, registered/enrolled nursing and physiotherapy, appeared to drive the inverse relationship between nursing and allied health service time. Registered/enrolled nursing service time was more sensitive to changes in physiotherapy rather than the other way around. Conclusions: The higher labour turnover among allied health staff compared with the nursing staff reported by the agency implies a substitution of labour between the two professions to ensure that the needs of clients are met. Health policy makers and health care professional educators need to acknowledge that workforce shortages will inevitably reshape professional boundaries. Leaving labour-force substitution undiscussed and unplanned may compromise the quality and safety of care.