The purpose of this research was to estimate (1) the extent to which institutional inbreeding is prevalent among mathematics faculty at colleges and universities throughout the United States; (2) the extent of institutional inbreeding among mathematics faculty at American colleges and universities classified according to institutional genre; (3) the extent of institutional inbreeding among mathematics faculty classified according to gender; and (4) the extent of institutional inbreeding among mathematics faculty in American colleges and universities classified according to regions of the country. Institutional inbreeding was defined as faculty employment at the institution from which one received the highest earned degree. An exhaustive review of the literature on inbreeding was used to develop this research. All public-supported and private-supported American universities that offer a doctorate in mathematics were identified by consulting the 1991 American Mathematical Society Professional Directory. Catalogs for the academic year 1991-1992 were requested from each institution. One-hundred sixty-seven institutions of higher education which offer the Ph.D. degree in mathematics and 5,961 faculty members were identified. The results of the analyses found a mean proportion of inbred mathematics faculty of 3.46 percent, which is one-tenth of the most recent study examining mathematics faculty. A chi-square goodness of fit test …