The use of semantically related words in new vocabulary lists is common practice in second language textbooks. However, research has suggested that organizing new foreign language vocabulary in semantic sets may cause interference and even slow acquisition as compared to other organizational methods (Erten & Tekin 2008). When it comes to assessing the frequency of this semantic organization of new vocabulary in foreign language textbooks, relatively little research has been done, especially with regard to Spanish textbooks. López-Jiménez's study (2012) on vocabulary in Spanish textbooks found that semantic organization was present in six of twelve textbooks surveyed, but the definition and measurement of semantic organization were not clear. Therefore, the present study seeks to improve this measurement based on a definition incorporating WordNet's online lexical database to calculate the semantic distance (using the Wu-Palmer method) between the words in each set. For this purpose, three textbooks used in the lower- and intermediate-level Spanish courses at Iowa State University were selected for analysis. To assess the levels of semantic relatedness within each set, the semantic distance calculations were then compared to a threshold determined by performing the same calculations on word sets that had been determined by the existing literature to be semantically related or unrelated. The results suggest that improvement can be made in the organization of words in each textbook and in the sample as a whole. Furthermore, a more precise definition is presented for determining semantic relatedness among vocabulary in foreign language textbooks. These results will be instrumental in helping to better inform the choice of materials for Spanish classrooms in the future.\nReferences:Erten, I. H., & Tekin, M. (2008). Effects on vocabulary acquisition of presenting new words in semantic sets versus semantically unrelated sets. System, 36, 407-422.López-Jiménez, M. D. (2012). A Critical Analysis of the Vocabulary in L2 Spanish Textbooks. Porta Linguarum, 21, 163-181.