The data collected in a 1978-79 study of 742 students enrolled in cooperative education (co-op) programs in forty-seven participating colleges and universities describes by sex what students in various fields of study do on their job, what they perceive their work conditions and responsibilities to be, how they view their abilities, and how their performance is rated by their employers. Students were divided into three groups according to the traditionality of their majors: female dominated (FD), neutral (NT), or male dominated (MD). Student logs, rating sheets, and a supervisor questionnaire/rating sheet were used to collect the data. Results indicate that working environment, conditions, events, and encounters are sex linked, as are the kind and amounts of personal and social interaction a student experiences on the job along with some attitudes and perceptions. Students majoring in fields where their sex is opposite to that of the dominant group resemble in many ways the members of the dominant group rather than others of their own sex. Supervisors generally agreed with students' self ratings; women's performance on the job was generally rated as superior to that of men. It was concluded that the first co-op experience is significant since it establishes and reinforces behavior patterns toward work and influences career development. (Study instruments and lists of participating institutions are appended.) (MED)