AbstractThe aim of the present study was to improve an occupational health program by means of systematic workplace investigations. The 8‐month study was done at three building sites of one construction firm. The method for workplace investigations was a simple job hazard analysis of chemical hazards, physical hazards, physical work load, mental stress, and risk of injury, each factor being rated on a three‐point scale. Information was gathered by observations, interviews, and a worker questionnaire. Occupational health and safety personnel and worker representatives dealt with problems cooperatively. Together they assessed occupational loads and hazards, whereafter the occupational health and safety personnel devised an occupational health care program and proposed preventive measures. The workplace investigation method proved to function well. It improved the occupational health care program, produced an overall analysis of occupational hazards, and dramatically increased the number and quality of proposed preventive measures. The new method was evaluated to be clearly superior to previous practices and was implemented at moderate cost. The study showed that attention to issues of environmental and occupational health can effectively prevent health impairment even in difficult settings such as construction work. More research is needed for effective utilization of information accumulated by systematic workplace investigati