The usefulness of proper preplacement physical examinations in reducing back injuries to workers on the job was discussed. One of the groups of workmen studied was a 5 year selected comparison group subjected to complete preplacement examinations including preemployment x-ray studies of the lumbar spine. The second group was nonselected nontraumatic back injured workers who had not been given preemployment x-rays. These nontraumatic injuries consisted of strain of muscle or ligaments and/or disk injuries. Of the 1,927 preplacement examinations, 424 persons were rejected due to x-ray findings. Only seven of the remaining 1,503 preplacement group acquired nontraumatic back strain on the job. Of the 3,395 workers who did not have preemployment x-rays, 254 nontraumatic injuries occurred over the same time period. Had these workers been subjected to preemployment x-rays of the lumbar spine, at least 952 days lost from work, 2,317 days disability, and about 112,000 dollars could have been saved. According to the authors, when obtaining the x-rays of the lumbar spine it is important that extreme care be exercised to properly center the films and position the patient so as not to give misleading information such as false narrowing of the intervertebral spaces, scoliosis, and pelvic tilt. Even so, the most careful screening cannot be expected to eliminate potential disk syndromes.