Setting priorities for workplace health and safety research depends upon accurate and reliable injury and illness data. All occupational health databases have limitations when used to summarize the national scope of workplace hazards. The comparison of data from multiple sources may produce more credible estimates of the leading occupational injuries and illnesses. The purpose of this paper is to describe the strengths and weaknesses of six data collection systems that record occupational injuries and illnesses on a national level and to compare the leading estimates from these systems for 1990. The six systems are: 1) National Traumatic Occupational Fatalities database, 2) the Bureau of Labor Statistics Census of Fatal Occupational Injuries, 3) The Bureau of Labor Statistics Annual Survey data, 4) a large workers' compensation database, 5) the National Council on Compensation Insurance data, and 6) The National Electronic Injury Surveillance System. Occupational injuries, as defined herein, predominate over illnesses in terms of the number of cases and the overall costs. Databases that provide information on the antecedents of injuries suggest how these injuries may be prevented and warrant more attention and refinement.