Science instructors and textbook authors often use analogies to help their students use information they already understand to develop an understanding of new concepts. This study reports the results of an analysis of the use of analogies in eight biochemistry textbooks, which included textbooks written for one-semester survey biochemistry courses for non-majors; two-semester courses for chemistry or biochemistry majors; and biochemistry courses for medical school students. We present an analysis of how analogies are used and presented in biochemistry textbooks, and we compare the use of analogies in biochemistry textbooks to the use of analogies in other science textbooks. We also compare the use of analogies in biochemistry textbooks with the factors known to promote spontaneous transfer of attributes and relations from analog concept to target concept.