In an attempt to determine whether certain physical characteristics discriminated between people with and without herniated lumbar discs, volunteers (N = 40) who were diagnosed as having a herniated lumbar disc were compared to control subjects (N = 40) who had been randomly selected and matched by age and sex. All subjects completed a questionnaire to determine the history of their back injury and a description of their exercise behavior patterns. Body composition was estimated by hydrostatic weighing. Maximum oxygen consumption was predicted using the Astrand-Ryhming nomogram. Strength scores were determined from a battery of cable tensiometer tests. Dependent variables were analyzed using a multiple analysis of variance (MANOVA). Using discriminant analysis, as a post hoc test, predicted maximum oxygen consumption was shown to account for the difference between the groups (P < .002). The control subjects'' values were higher than the patients'' values. Subjects'' exercise history indicated no differences between the groups relative to the time period preceding the onset of injury (P > .05). The exercise activity of patients was significantly reduced after injury (P < .001). An average of 87 days elapsed between the onset of injury to the date of fitness testing.