A case-control study of the risk of injuries incurred by male shipyard workers in Den Helder, The Netherlands, was carried out in 1986-1987. The main focus of interest was factors which can interfere with faculties needed for recognizing warning signals of imminent danger. Three hundred workers who had had at least one injury in the previous 3 1/2 years and 300 matched controls were asked about their current use of alcohol, tranquilizers, and cigarettes; the wearing of spectacles and earplugs; taking a nap at noon; engaging in sports during leisure hours; and involvement in a traffic accident during the past year. The hearing acuity of most of the workers involved in the study, as well as the noise load at work, had been recently assessed. Alcohol consumption, hearing loss greater than 20 dB, and loud noise greater than 82 dB(A) were found to be safety hazards. At this shipyard, the risks attributable to noise and hearing loss together accounted for 43% of the injuries.