We investigate the determinants of application for Social Security Disability Insurance (DI) benefits in approximately 45 jurisdictions between 1981 and 1999. We reproduce findings of previous studies of the determinants of DI application then test the additional influence of changes to workers’ compensation program benefits and rules on DI application rates. Our findings indicate that the programs are interrelated: When workers’ compensation benefits declined and eligibility rules tightened in the 1990s, the DI application rate increased.