Abstract: The Federal Sentencing Guidelines were promulgated in response to concerns of widespread disparities in sentencing. After almost two decades of determinate sentencing, the Guidelines were rendered advisory in United States v. Booker. How has greater judicial discretion affected interjudge disparities, or differences in sentencing outcomes that are attributable to the mere happenstance of the sentencing judge assigned? This Article utilizes new data covering almost 400,000 criminal defendants linked to sentencing judges to undertake the first national empirical analysis of interjudge disparities after Booker. The results are striking: Interjudge sentencing disparities have doubled since the Guidelines became advisory. Some of the recent increase in disparities can be attributed to differential sentencing behavior associated with judge demographic characteristics, with Democratic and female judges being more likely to exercise their enhanced discretion after Booker. Newer judges appointed post-Booker also appear less anchored to the Guidelines than judges with experience sentencing under the mandatory Guidelines regime. Disentangling the effects of various actors on sentencing disparities, I find that prosecutorial charging is likely a prominent source of disparities. Rather than charging mandatory minimums uniformly across eligible cases, prosecutors appear to selectively apply mandatory minimums in response to the identity of the sentencing judge, potentially through superseding indictments. Drawing on this empirical evidence, this Article suggests that recent sentencing proposals calling for a reduction in judicial discretion in order to reduce disparities may overlook the substantial contribution of prosecutors.