This descriptive longitudinal study based on Nagi's theory of the disabling process tested an explanatory model of the relative influence of biologic, environmental, and behavioral/lifestyle risk factors on each other and on postinjury disability after non-central nervous system traumatic injury. Data are reported on the sample of 109 subjects who remained in the study through 3 months post-hospital discharge. Subjects experienced a fairly severe level of injury (mean injury severity of 15.5; mean of number of injuries 4.4) and are representative of an urban trauma population. The trimmed explanatory model demonstrated that 67% of the variance in postinjury disability was accounted for by postinjury functional limitations, post-traumatic psychological distress, pre-injury disability, and age. Age indirectly influenced postinjury disability through its effects on pre-injury functional limitations and pre-injury disability. Social network indirectly influenced disability through its effect on post-traumatic psychological distress. Patients whose maximal injuries involved the extremities and pelvic girdle had significantly higher levels of postinjury functional limitations than those with maximal injuries involving any other body system.