This proposal describes case-control studies of the epidemiology of prolapsed lumbar intervertebral disc and prolapsed cervical intervertebral disc, musculoskeletal conditions accounting for a great deal of disability and economic cost in the United States. Putative risk factors of particular interest include driving of motor vehicles, frequency and methods of lifting heavy objects and other activities on the present and previous jobs, frequency and methods of lifting heavy objects other than on the job, exposure to vibration, and smoking and coughing. Exposure to possible risk factors among surgical, probable, and possible cases of each of these conditions in the age range 20-64 years will be compared to exposure to possible risk factors among a control group without known spinal disorders matched to the cases by age, gender, and facility at which care was sought. Persons with previous prolapsed discs or other significant back or neck problems or with symptoms for more than one year will be excluded from the case and control groups. Information on symptoms, exposure to possible risk factors, and demographic variables will be obtained by means of a structured questionnaire administered by trained interviewers. Since the extent of exposure to the risk factors of interest can be modified, such as by design changes in motor vehicle seats, by changes in lifting requirements on jobs, and by further education on optimal methods of lifting both on and off the job, it is hoped that the results of this study will lead to a decrease in the frequency of occurrence of prolapsed discs.