The purpose of this study was to clarify the concept of expertise among occupational health nurses. The material consisted of 24 research articles and one theory article published between 1983 and 1997. These were analysed using Rodgers’s concept analysis model. The analysis revealed that the surrogate term was authority, and the related concepts were specialist, professional, practitioner and generalist. The attributes of the concept of expertise were associated with roles, profession, position, title and functions. The antecedents of the expertise were identified as knowledge and skills, education, training, experience, personal characteristics and work-related opportunities. The consequences of the expertise were economic and health benefits. Most commonly, the expertise of occupational health nurses referred to clients, workplaces and health-care units. Changes in the concept of expertise were also examined and a definition of expertise formed. Concept clarification is necessary for the development of occupational health education, practice and theory building.