The content of high school biology courses is overwhelming in quantity. This coverage does not permit students to engage in inquiry whereby they construct knowledge in a meaningful manner. Initially, the study sought to identify a small list of essential topics as the focus of high school biology. With the help of seven science supervisors in a large metropolitan area in the Southwest who have taught high school biology for many years, the problem of course content was examined. After three separate contacts by mail to the supervisors using a Delphi technique, a view emerged: Teach students the big ideas of biology rather than specific topics, but use topics to develop the major themes and unifying principles. These findings need to be discussed with biology teachers to help them focus their teaching on a smaller body of course content that relates directly to the major ideas of biology.