To develop a more scientifically literate society, students need to understand the nature of science, which may be affected by controversial topics such as evolution. There are conflicting views among researchers concerning the relationships between understanding evolution, acceptance of evolution, and understanding of the nature of science. Four instruments were administered to undergraduate biology students (majors and nonmajors). As expected, biology majors had a greater knowledge of natural selection, acceptance of evolutionary theory, and understanding of the nature of science than nonmajors. Multiple regression was used to indicate which variables significantly predict students' understanding of the nature of science. Significant predictors for majors included acceptance of evolutionary theory and understanding of natural selection and explained 42.8% of the variance. For nonmajors, in addition to these two variables, attitudes toward biology and parents' level of education explained 24.1% of the variance. Implications for improved education strategies are discussed.