The United States and six other countries (Germany, Denmark, Norway, Sweden, Israel, and the Netherlands) are participating in a cross-national study of work incapacity and reintegration under the auspices of the International Social Security Association. The purpose of the study is to identify those medical and nonmedical interventions that are most successful in helping persons disabled due to a back condition return to work. The study involves a baseline survey and two follow-up surveys over approximately 2 years. This article reports on the findings from the baseline survey conducted in the United States. It compares the responses of persons from four study groups (the Social Security Administration's Disability Insurance (DI) beneficiaries and Supplemental Security Income (SSI) recipients, and temporary disability insurance (TDI) recipients from two States--California and New Jersey). The article discusses the potential influence of certain characteristics on the capacity for work reintegration. Study findings suggest that the characteristics of TDI recipients with back disorders may differ in some respects from those of recently entitled DI or SSI beneficiaries with similar impairments, and that there may be some correlation between work resumption and factors such as education occupation, work-related demands, and the presence of other chronic diseases.