This paper constitutes an attempt to establish the criteria used by the most important monolingual dictionaries of Spanish language, published in the nineteenth century, in order to introduce neologisms. For achieve this objective, I start from the collection of neologisms compiled by V. Salvá in his Nuevo Diccionario de la Lengua Castellana (1846), contrasting his labour whit that developed by the others lexicographers of this period and, very specially, with the different issues of the DRAE in the nineteenth century.