The problem in this investigation was to determine if there is a significant difference in the mean level of achievement in Physical Science Study Committee (PSSC) physics between students using autoinstructional materials, supervised by a physics teacher, and students studying PSSC physics without such materials, under the guidance of a physics teacher. Six high schools supplied the 66 students for the experimental group and 105 students for the control group in a six-month study. Students of the experimental group used autoinstructional materials written for parts I and II of the second (1965) edition of PSSC as compared with the control group who were taught PSSC physics by their teacher in a conventional manner. With physics achievement scores for both groups adjusted for covariates, the experimental group demonstrated a statistically higher mean level. From student and teacher responses, several strengths to the autoinstructional mode of instruction were identified. (Author/CP)