This study was undertaken to determine the effects of individualized instruction on enrollment, attrition, achievement, and student attitude in a general biology course for non-science majors. Fifteen auto-tutorial minicourses were designed for use in the laboratory part of the course, each consisting of a printed study guide, slide-tape module, laboratory exercise, grade-option activity, objective post-test, and evaluation. Data from the classes receiving conventional instruction during the spring of 1977 were compared to data gathered during the fall semester using auto-tutorial instruction. Results showed that enrollment and student retention were improved using auto-tutorial instruction. Final grades received by the experimental group were significantly higher than those achieved by students in conventional classes. A direct correlation was shown between time spent in the laboratory and final grades. Students' attitudes were positive about auto-tutorial instruction and the minicourses, which were found to be of generally good quality, contributed to the learning of the students. Although no preference for either type instruction was shown by the auto-tutorial students, the students in conventional classes favored that type of instruction. (VT)