The author discusses the vices, virtues, and problems of mass instruction in college sociology. His observations are based on personal experience. A "mass" class is defined as one with an enrollment exceeding 250 students who meet together as a class at least part of the time. Sociologists generally believe that mass classes are not a good form of instruction, but use them because they are a cost effective means of dealing with large enrollment courses and because they concentrate the burden of lower division teaching on one or a few instructors. The perceived vices of mass instruction are well known: student anonymity and social distance from instructor, reduced motivation to learn, and the tendency to focus instruction on the lowest cognitive levels. The practical problems of mass instruction can be classified under three headings: problems of scale; problems of space, equipment, organization, and time; and personal problems of and for the instructor. A number of specific examples of problems in each category are discussed. Perhaps the most persistent and difficult problem for the instructor is that a significant number of students will always perceive the quality of instruction in the mass class as inadequate. The principal reason that mass teaching is problematic is the lack of an appropriate theoretical model for doing it. All educational models for instruction are based on the assumption that a class is a social group which interacts on the basis of reciprocal normative expectations. The mass class, however, is an audience, i.e., a collective behavioral phenomenon, not a group. Thus theater might offer a better model for defining its instruction, but this possibility has not been explored. The paper closes with sets of observations and advice about mass teaching directed to departments that use or consider it. (Author/RM)