These are two major models for advanced science instruction in American high schools, the traditional honors program and the Advanced Placement (AP) program of the College Entrance Examination Board. Using the self-reports of teachers who were experienced in teaching honors and AP courses to students of similar academic preparation and ability, the author examined the perceived influences of program format upon the use of basic teaching techniques, the laboratory experience, the pace of the course, curricular freedom, and student creativity. One of the most notable aspects of the AP program is the speed at which teachers move through the curriculum. In the rush to prepare students for the exam, most AP teachers adopt a strong lecture format and minimize student-centered activities such as laboratory experimentation, student projects, and student presentations. When laboratory work is not assessed on the national AP examination, such experiences are sacrificed to provide time for lecture. When laboratory experiments are assessed, however, teachers respond by allocating more time for laboratory work, and by upgrading their exercises to make them more quantitative and experimental than those used previously or those used in honors classes. Although AP is associated with a loss in curricular freedom and flexibility, teachers perceive no clear influence of program format upon student creativity.