A few attitudinal and behavioural principles will bring about a productive liaison between the occupational physician and trade unions. An effective working relationship with these organizations and employee associations can be developed, provided the occupational health care professionals are impartial in their practice, the loyalty to medicine replacing any bias toward the favouring of a managerial view. Respect must be given union officials, for in their organization they have status and can advance or defeat various health programs. Union representation on an occupational health committee will gain union support and minimize the filing of health-based grievances. The presentation of occupational health information at union meetings will communicate the goals of in-plant programs and familiarize workers, through their accustomed channels, with the objectives of health care policies and procedures.