The purpose of this study was to compare the characteristics of teaching performance in accordance with the opinion of students of different academic fields and curriculum stages in a Mexican state public university. The sample was composed of 729 randomly-selected courses, distributed over four semester periods. Descriptive and comparative statistical analyses were made. The results determined significant differences when natural-exact sciences were compared with administrative sciences (p = .003), and engineering with administrative sciences (p = .022) in the overall ratings and by dimension. Moreover, differences were found in the ratings by dimension between the curriculum stages. The study concludes in favor of considering the particularities of the pedagogical context in the interpretation of ratings, and of using them as a source of information when designing strategies for improving teacher training. In the university, the evaluation of instruction plays a determining role in advancing the quality of learning. Key documents of Mexican and international educational policy recognize that instruction is important in achieving educational quality (Asociación Nacional de Universidades e Instituciones de Educación Superior, 2007; Anderson, 2004). The importance of evaluating instruction stems from its potential as a tool contributing to teachers' becoming professional and thus, improving their training. Teacher evaluation based on Student Evaluations of Teaching (SETs) effectiveness is characterized by two particularities: it is the strategy most often used in North America, Europe and Asia, and is also the one most studied (Theall & Franklin, 2000; Seldin, 1993). In this context, two situations stand out regarding rating forms: first, there is a good deal of evidence for the misuse of the ratings students give; and second, teachers show a growing unease about the use of these ratings in the making of administrative decisions. A great part of the criticism regarding rating instruction concerns the procedures of application, interpretation, and use of the results (Sproule, 2000; Díaz-Barriga, 2004). In particular, one of the most frequent errors related to the interpretation of the results is the aggregation of all the teachers' ratings without consideration for the particularities of the pedagogical context, such as the disciplinary field in which they teach and the educational stage. The purpose of this work is to compare the characteristics of the teacher's performance, according to students' opinion, by disciplinary field (natural-exact sciences, engineering and technology, and administration sciences), and curriculum stage (basic and disciplinary/final stages). The objective is to contribute to the discussion regarding the interpretation and the use of the results of students' evaluations of university teaching. In Mexico, as in other countries, the evaluation of teaching has resulted from social demands coming from different audiences with heterogeneous needs of evaluation and has been linked to the establishment of federal policies in this area. Until the end of the eighties, the evaluation of instruction was conducted primarily because of the institutions' need to obtain information on the quality of teaching and, in theory, to provide feedback on the strategies of teacher training (Arias, 1984; Luna, 2002). Since 1990, with the widespread implementation of merit pay programs, the evaluation of teaching has been included as one of the indicators of these programs. Hence, attention has been given principally to the need for administrative control over instruction (Canales & Gilio, 2008). Today, expectations for the evaluation of teaching are diverse: teachers and students expect fair and appropriate systems to improve teaching; the authorities seek to have better information for administrative decision making, allocation of courses, promotions and economic incentives; and governmental institutions seek a means of accountability for the quality of instruction (Luna, 2004; Secretaría de Educación Pública, 2007). In Mexico however, research on the evaluation of university teaching is a recent development and is still in its infancy. The investigation into the evaluation of instruction began after evaluation policies were instituted at the beginning of the nineties, and it was in 1996 that the systematic production of literature regarding the topic began (Luna & Rueda, 2008). This is unlike the situation in other countries where there is a long history and tradition regarding SETs. Furthermore, the Mexican State has promoted an evaluation of teaching associated with policies of control and wage compensation, and as a result, this type of assessment has idiosyncrasies which have transcended research—for example, the difficulty of creating evaluation procedures apart from control.