Accidents on construction sites are a major cause of morbidity and mortality in Hong Kong. We studied 122 injured construction workers in a hospital and an equal number of workmate controls. Data on injuries were obtained from medical records in the hospital. Personal and occupational data were obtained from the cases by interview. Similar data were sought from controls. Single injuries were seen in 80% of cases. Of 149 injuries classified by body region, 49% were external, 26% involved either the upper or lower extremities, and 11% were spinal injuries. Healthcare and compensation costs per capita were high. Working at height was associated with the injury severity score. Safety hazards were identified in the work environment in 68% of cases. Significant odds ratios for accidents were obtained for no formal education, no safety training and current smokers. Much needs to be done in improving the work environment and promoting safety education among construction workers.