We present the first causal estimates of the effect of Social Security Disability Insurance benefit receipt on labor supply using all program applicants. We use new administrative data to match applications to disability examiners, and exploit variation in examiners’ allowance rates as an instrument for benefit receipt. We find that among the estimated 23% of applicants on the margin of program entry, employment would have been 28 percentage points higher had they not received benefits. The effect is heterogeneous, ranging from no effect for those with more severe impairments to 50 percentage points for entrants with relatively less severe impairments.