Several recent reports concerning the status of science education in K-12 classrooms have emphasized the centrality of textbooks to instruction. Some initial investigations of the nature of textbooks have suggested that typically more new words and terms are introduced than one would expect to find in a similar time frame as foreign languages are studied. This is a review of these initial studies, a review of the studies of mastery of vocabulary in foreign languages, and a review of general research concerning the vocabulary development, especially as it pertains to reading. Twenty-five of the most commonly used textbooks in K-12 science classrooms are analyzed in terms of the occurrence of special/technical words. The number of words introduced at every level is considerable-often more than would be required if a new language were being introduced. In addition, the number of new words in science often approaches the total number that could be expected in terms of total vocabulary increase at a given grade level for a given student. There is strong evidence that one major fact of the current crisis in science education is the considerable emphasis upon words/terms/definitions as the primary ingredient of science-at least the science that a typical student encounters and that he/she is expected to master.