In the current study, nine participants were asked to make gender decisions for a set of Spanish nouns while being scanned with functional MRI (fMRI). Words were chosen in which a direct mapping between ending and gender ("transparent" items such as carro(fem) or casa(masc)) is present and those in which there is not a direct relationship ("opaque" items such as fuente(fem) or arroz(masc)). Direct comparisons between opaque and transparent words revealed increased activity in left BA44/45, and BA44/6 as well as bilateral activation near BA 47/insula and the anterior cingulate gyrus. These results reveal activity in areas previously found to be devoted to articulation of the determiner and to morphological processing. Taken together they support the notion that gender decisions for opaque items requires deeper and more effortful processing during the retrieval of lexical and syntactic information.