Factor analyses of student evaluations of teaching effectiveness were conducted for 24,158 courses at the University of Southern California and for each of 21 different subgroups derived from the total group. All classes evaluated by six or more students were included in the study. The subgroups were designed to differ in terms of instructor level (teaching assistants or regular faculty), course level (undergraduate or graduate), and academic discipline. The same 9 factors that the Student Evaluation of Educational Quality instrument was designed to measure were consistently identified in each of the 22 different factor analyses, and all factor structures were remarkably well-defined and consistent. Correlations between factor scores based on the total group factor analysis and the 21 subgroup factor analyses were very high, and most were greater than 0.99. Because of the large number and diversity of classes in this study, the results provide stronger support for the generality of the factor structure underlying students' evaluations of teaching effectiveness than does any previous research. Five data tables are included. (TJH)