Recognizing the importance of reflection about teaching as a fundamental activity to promote faculty development, the present research was conducted to: 1) explore the practices of instructional reflection of four undergraduate level professors at the University of Puerto Rico (UPR), 2) understand how these practices influence their teaching and professional development, and 3) analyze their reflective practices based on traditional theories of reflection, namely Dewey's Reflective Theory, the Critical Thinking Movement, Schön's Reflective Practitioner Model, Critical Pedagogy, and Mezirow's Transformative Learning. A qualitative, multiple-case study was designed for this study, with interviews and observation of classes. Collected data were transcribed, categorized and coded; findings were presented in narrative form. Among the results stands out that professors critically examine their teaching practices through: 1) dialogue with colleagues and students, 2) reading of various types of materials, 3) writing about their teaching, 4) peer class observation, and 5) analyzing course evaluations and program assessment results. From their testimonies it also follows that reflection influences their teaching and professional development because they: 1) privilege questioning and critical dialogue as instructional strategies par excellence, 2) democratize their classrooms, 3) continuously update their courses, 4) experiment with new assessment strategies; 5) promote active learning and 6) create new courses. Classical theories of reflection converge in the professors' reflectivity. In addition, they integrate elements from other theoretical perspectives–e.g. feminism, Queer Theory, postmodernism, general education, and inter and transdisciplinarity– with which they enhance and reinvigorate their instructional reflection. Of potential interest for university academic leaders was the finding that, in general, participating professors understand that their reflective practices occur in spite of, and not supported by, the university administration, which they perceive as disconnected from the real needs of teachers and students.