Doctoral programs in the humanities and related social sciences are characterized by high attrition and long times to degree. In 1991 the Andrew W. Mellon Foundation launched the Graduate Education Initiative (GEI) to improve the quality of graduate programs and in turn reduce attrition and shorten time-to-degree. Over a 10-year period, the Foundation provided approximately $58 million to 54 departments at 10 major research universities. We estimate the impact of the GEI on attrition rates and time-to-degree using competing-risk duration models and student-level data. The data span the start of the GEI and include information for students at a set of control departments. We estimate that the GEI had modest impacts on student outcomes in the expected directions: reducing attrition rates, reducing time-to-degree, and increasing completion rates. The impacts of the GEI appear to have been driven in part by reductions in entering cohort size, increases in financial support, and increases in student quality.