This report uses data primarily from the 2004 Graduation Rate Survey (GRS), a component of the Integrated Postsecondary Education Data System (IPEDS), to provide a systemwide overview of how graduation rates of comparable 4-year institutions vary with institution selectivity and the size of the low-income population enrolled. The report clearly shows that graduation rates dropped systematically as the proportion of low-income students increased, even within the same Carnegie classification and selectivity levels. Variations by gender and race/ethnicity also were evident. Women graduated at higher rates than men, and in general, as the proportion of low-income students increased, so did the gap between female and male graduation rates. The gap in graduation rates between White and Black students and between White and Hispanic students, on the other hand, typically narrowed as the as the proportion of low-income students increased. In the end, the results indicate that serving large numbers of low-income students does not necessarily lead to low graduation rates. Appended are: (1) A Glossary; and (2) Technical Notes and Methodology. (Contains 14 tables and 8 figures.)