This report presents results of Personalized System of Instruction (PSI) during the fall 1972 semester in an introductory Biology class at North Country Community College. Fifty-seven students were enrolled in the course at the beginning of the semester. Course content was divided into 20 units of study. A study guide was written for each unit containing introduction, behavioral objectives for the unit, and a suggested procedure for objective mastery. Five student proctors (tutors) assisted students to master course content. Of the initial group of 57 students, 22 were classified as withdrawals. Course evaluation by the students tend to indicate a favorable response to PSI. Progress charts, statistical data, and evaluation results are included. (MJM)