The presentations of evolutionary theory in 13 prominent, secondary-school biology textbooks—3 Chinese, 8 American, and 2 Soviet—were examined using the methods of content analysis. For each book, the amount of text devoted to each of 80 evolutionary topics was assessed. Such word counts were enumerated not only for the main narrative, but also for eight supplemental components (illustrations, marginal information, appendixes, etc.). Pronounced differences in topic emphasis among the 13 textbooks and systematic trends between countries are discussed. The strong emphasis on evolution in the USSR textbooks is impressive, but these textbooks also neglect some major themes, and they devote considerable text to certain concepts of an erroneous or dubious nature. The PRC (People's Republic of China) textbooks fail to introduce a considerable number of topics that are prominent in the other two systems. The eight USA textbooks exhibit great diversity in terms of total evolutionary content, number of themes treated, and which topics are emphasized. Unlike the USSR and PRC textbooks, the USA books position a vast amount of evolutionary content (26.5%-55.8%) within components outside the main narrative. The evolutionary text of USA editions is dispersed throughout and is presented surprisingly early. Several individual themes that proved particularly revealing are examined, including human evolution, law of recapitulation, evolution and religion, evidences of evolution, punctuated equilibria, and artificial selection.