In spite of the importance of geological time in evolutionary biology, misconceptions about historical events in the history of life on Earth are common. Glenn (1990) has documented a decline from 1960 to 1989 in the amount of space devoted to the history of life in high school earth science textbooks, but we are aware of no similar study in biology textbooks. Given the overall reduction in evolution coverage in biology texts (Rosenthal,1985), we might expect the treatment of historical aspects of evolutionary biology to be limited. In this article, the authors present the results of a survey of 11 high school biology textbooks in which the following questions were addressed: (1) To what extent do texts discuss the logical processes and historical inferences that support many of the claims relating to evolutionary biology?; (2) How extensive is the coverage of geological time and the biological events that occurred at various points in the history of life on Earth?; and (3) What kinds of timelines or other graphic devices do textbooks use in their descriptions of evolutionary events? Many of the texts reviewed here include activities that model the geological time scale using clothesline or adding machine tape or toilet paper. These are concrete experiences that can accurately depict the relative time periods and help students appreciate the magnitude of geological time. The National Council for Social Studies "Curriculum Standards for Social Studies" (1994) encourages the use of timelines to help students acquire information and to set historical events in relation to one another. Timelines that truncate Precambrian time, or omit it altogether, will perpetuate these misconceptions and limit the student's understanding and appreciation of the great events of deep time. An accurate view of the geological time scale will enable biology teachers to reduce the number of misconceptions concerning the history of life on Earth. (Contains 2 tables.)