In the Dutch Working Conditions Act, every employer is required to organize preventive occupational safety and health services (OSH-Services). The OSH-Services need to have a certification that can be compared with ISO-9000. This article is focused on the question: How can companies and OSH-Services co-operate more effectively to obtain a better OSH management system inside the companies? To answer this question, TNO has developed an approach to support organisations in the health care branch to obtain a better service from their OSH-Service. TNO has chosen to focus on supporting the companies, because of the recognition that the effectiveness of OSH-Services has been found in effects on their customers, the companies. As a result of the research project a stepwise approach with several tools was developed. After the development phase, parts of the approach and the tools were used in several other consultancy projects. Evaluative studies have not been performed yet. However, from the development activities and several consultancy projects some remarkable evaluative findings can be given. The approach can be useful for companies and OSH-Services to make their goals and expectations more explicit. The approach also helps to make the management of companies clear that their own behaviour is relevant to the achievement of their goals in occupational health and safety policy, in addition to the services provided by the OSH-Service and their professionals. The approach cannot fulfil the possible need for qualification of OSH professionals. However, the approach can make the OSH professionals clear in what way they have qualification needs.