While school textbooks are assumed to be written for and used by students, it is widely acknowledged that they also serve a vital support function for teachers, particularly in times of curriculum change. A basic assumption is that biology textbooks are scientifically accurate. Furthermore, because of the negative impact of "misconceptions" on learning, it is desirable that textbooks point out common misconceptions and why they are scientifically unacceptable. This paper reports on a study of life sciences textbooks as a potential influence on misconceptions about evolution by natural selection. Textbooks for Grades 10 to 12, from two different publishers, were investigated using content analysis to establish, first, the nature and extent of scientifically incorrect statements about evolution; second, latent problems with wording which might lead to unscientific ideas; and third, whether the books identified and addressed common misconceptions. Unscientific statements were found in all six books, but latent problems associated with the way explanations were expressed were also considered to pose a significant threat to learning. While particularly important for textbook authors and publishers, these findings are also of value to teachers. Although this study was conducted in South Africa, the findings provide useful insights for a wider audience of biology education stakeholders.