Associational vocabulary knowledge is associated with writing and speaking skills. These skills are essential for EAP students who express themselves in oral presentations or written assignments. Therefore, diagnostic measurement of associational vocabulary knowledge is of vital importance, especially in regard to the most frequent 1,000 word families that cover 81% and 85% of written and spoken text. This study measured 46 Iranian EAP students’ productive semantic associational knowledge of words at the 1,000 word frequency level. The findings indicate that while participants had productive form-meaning knowledge of the words, they did not seem to have extensive semantic associational knowledge of the same words. This assists in diagnosing area of weakness and the degree to which instructional emphasis on high frequency words might improve their knowledge.