Although secondary school principals may believe that instructional leadership should be their most important role, many complain about their inability to succeed in this endeavor. They typically cite as reasons the numerous other tasks needing their everyday attention. After briefly summarizing recent research substantiating instructional improvement as principals' primary responsibility, this paper reports survey results from a random sample of 721 public high school principals in Ohio. Questionnaires were mailed to 130 principals; 122 were returned, and 116 were analyzed. Respondents were asked to rank 14 reasons that hindered or prevented them from working on instructional improvement. Data analysis revealed that Ohio principals perceive two major obstacles: (1) the time spent handling student discipline problems and (2) faculty resistance to new instructional improvement ideas. None of the other reasons was selected by more than 50 percent of the respondents. Demographic factors (age, years of experience, and school enrollment) appeared to be unrelated to principals' selections. If data gathered from other states support these results, steps must be taken to remedy or eliminate the two impediments to Ohio principals' instructional improvement efforts. Included are a sample questionnaire and five references. (MLH)