The paper discusses retention models for the nontraditional student population, including transfer students, older adult learners, commuters, part-time students, graduate students, women, students with disabilities, and ethnic minorities. Since 1975, leading research in the field of postsecondary student retention has been grounded on Tinto's (1975) argument that the student-institution "fit," or the students' social and academic integration into the institution, is a good predictor of dropout or persistence. Other models of student retention focus on student involvement and the institution's responsibility to promote student retention. In the 1980s, attrition models were modified to address some of the shortcomings of previous schema. Similar to traditional student models, most models that try to predict non-traditional student retention are concerned with student-institution "fit." Benjamin's "Quality of Student Life" model, however, focuses on conceptualizing satisfaction as a multidimensional construct involving the interaction among personal, interpersonal, social and contextual factors and/or processes. It attempts to grapple with the complex and dynamic nature of students within postsecondary systems, and recognizes that competing demands of parents, friends, romantic partners, employers, and others, as well as financial and health problems, can influence students' coping abilities and life decisions. Discussed are the challenges faced by particular groups of non-traditional students, and the factors that affect the attrition rates of these students. Contains 164 references and 18 figures. (JA)