Aims. The aims of this study were to describe Finnish occupational health nurses' functions, characteristics, prerequisites, consequences, changes, development areas and expertise from the point of view of clients. Methods. The background literature of this study is based on public health nursing models, Finnish social and health report, arguments of special education for occupational health nurses, and earlier studies concerning occupational health nurses' work. The data were collected from volunteer clients (n=26) by interviews. Results. According to the qualitative content analysis, occupational health nurses' activities include health promotion and secondary health care among workers and at workplaces. The main work characteristics are holism, client-orientation, interaction and co-operation. Occupational health nurses need an extensive knowledge base and practical skills, client-orientation, courteous behaviour and a healthy and clean appearance. The outcomes of their work for clients are better health, healthier life habits and healthier working conditions. Nowadays, nurses are more client-orientated than 20 years ago. They are expected to develop their practical and interaction skills and expand their knowledge base. The expertise of occupational health nurses consists of an extensive knowledge base with practical skills, working experience and confidence, and it appeared when advising clients and answering their questions. Conclusions. It is important to arrange continuing education for occupational health nurses to ensure that they are always up to date in order to be able to respond to specific clients' needs. This study provides a foundation for further investigations into, for example, occupational health nurses' work from the point of view of employers, students of occupational health nursing and other occupational health experts and co-operative partners.