The extent of use of the Personalized System of Instruction (PSI), also called the Keller Plan, at a large university campus was investigated. Attention was also directed to the features of PSI used: mastery criterion, self-pacing, proctors, number of times students could retake an exam, and the number of forms of each examination used. The PSI includes clearly delineated objectives or study guides, formulated by the instructor, and presented to the students as a series of units arranged in hierarchical order. From this material students learn, usually without lectures. Of 115 full-time faculty members who were sent a questionnaire, 85 responded. Eighty-one percent of the respondents used the lecture method, and usage ranged from 100 percent by the natural sciences and engineering department to a low of 68 percent in the humanities department. The seminar/discussion method was used by 27 percent of the respondents. The humanities faculty used this method the most (50 percent), and the engineering faculty the least (0 percent). Many faculty used lectures for lower-level classes, and seminar/discussion for upper-level classes. PSI, the least used method, was used by faculty in the behavioral sciences (33 percent) and business (10 percent). Only 18 percent of the respondents had ever used the PSI. The PSI features most often used were self-pacing, a mastery criterion, and the use of several versions of the exam over each unit. The questionnaire is included. (SW)