This study presents the results of three experiments in which the Family Size (FS) effect is explored. The first experiment is carried out with no prime on simple words. The second and third experiments are carried out with morphological priming on complex words. In the first experiment a facilitatory effect of FS is observed: high FS targets produced faster responses than low FS targets. However, an inhibitory effect of Stem-FS is observed in the second experiment: low Stem-FS targets produced faster responses than high Stem-FS targets. In the third experiment a facilitatory effect is observed when the Affix-FS is manipulated: high Affix-FS targets produced faster responses than low Affix-FS targets. Overall data confirms that the effect of FS plays an important role in lexical access in Spanish. The results also show that the effect of FS is modulated by the lexical nature of the prime (lexical or sublexical) and by the number of candidates activated. Finally, it is suggested that the nonwords employed were decisive in obtaining the results mentioned.