Previous research on principals as instructional leaders has been confined mostly to elementary schools and has disclosed little information regarding the specific behaviors used by principals in instructional leadership roles. This study focuses on high school principals' behaviors and attempts to determine the behavior differences between principals of "effective" and regular high schools and the effects of selected variables (school size, years of experience, and number of assistant principals) on the behaviors of principals in effective schools. Survey methods were used to collect data from a random sample of 200 Ohio high schools. Principals and chairpersons of 107 schools participated. The study used a three-part instrument designed to gain background information, respondents' perceptions concerning the presence or absence of effective school factors, and measure the extent of principals' engagement in various direct and indirect instructional leadership behaviors clustered into five separate scales: staff development, teacher supervision and evaluation, instructional facilitation, resource acquisition and building maintenance, and student problem resolution. All principals indicated that they at least sometimes engaged in all 30 behaviors included in the Instructional Leadership Behavior Questionnaire (ILBQ). High school principals tend to engage in more indirect than direct instructional leadership activities. Overall ILBQ scores were higher for principals from "effective" high schools. Included are 22 references and an appendix listing instructional leadership behaviors reported by high school principals. (MLH)