In this paper we present the results obtained when evaluating the Natural Numbers Recognizer of Telefónica I+D over some particular dialects of Spanish from Spain and America. The evaluation was made over two different data sets corresponding to two different situations. A first set includes dialects of Spanish from Spain, that were considered in the training and design of our baseline system, and a second set corresponds to Argentinian Spanish, that was not considered to train the original system. Just because we are interested in a system able to be used by a wide range of users, we tested the possibilities of MAP (Maximum-A-Priori techniques) to adapt the original HMMs in order to represent all the dialects. The experimental results show the capabilities of our recognizer to be used in applications spread over a great number of Spanishspeaking countries.