Background and Aim: Setting of candidates for a word with similar beginnings is known as the Cohort size. Despite the importance of the number and properties of candidates in word recognition, so far, in none of the tests made for Persian language, the Cohort size is considered. The purpose of current study was the introduction of importance of Cohort size in word recognition and calculation of Cohort size for the list of Persian high-frequency spondee words.

Methods: The spondee words extracted from high-frequency Persian word store. Then, total spondee words with same first syllable in Amid Persian dictionary recorded and Cohort size calculated for each spondee word. Thus, the list of high-frequency spondee words with their Cohort size composed of 4121 words obtained.

Results: The Cohort sizes of word had a wide range from 0 to 87. In the half of the words, the Cohort sizes were less than 14 and in the rest were more than it.

Conclusion: The Cohort size affects the time course and precision of decision making about words. Persian words are not equal in Cohort size. For having more controlled test materials to develop and design different types of auditory tests, it is possible to consider the Cohort size of words along other effective factors.