In the North American English language there is a phonetically balanced (PB) word corpus for measuring speech intelligibility which has been standardized by ANSI and is correlated with measurements of STI. In the Spanish language little has been done in the development of list of words that fulfills the same ANSI objectives. Starting from the correlation established for English, the behaviour of two lists of words that measures intelligibility is analyzed. As a result, the equation that relates the percentage of intelligibility of each list in relation to the measured STI is given. It is concluded that intelligibility measurements differ from the lists used, and that none of the Spanish corpus is correlated with the STI as it occurs with the English corpus normalized by ANSI.