This paper develops a dynamic programming model of the Social Security Disability Insurance (SSDI) application timing decision. We estimate the time to application from the point at which a health condition first begins to affect the kind or amount of work that a currently employed person can do. We use Health and Retirement Study (HRS) and restricted access Social Security earnings data for estimation. Our results show that the type of work-limiting health condition, presence of employer accommodation, and the relative value of income in the application state to income in the work state significantly affect the timing of SSDI application. Copyright © 2004 John Wiley & Sons, Ltd.