|Abstract:||In this thesis I contend that the variability observed in hypocoristic truncation and reduplication in Spanish is predictable and, therefore, grammatical. I argue that the output structure of truncates and reduplicants is a compromise between phonological markedness and faithfulness, and that the two Prosodic Morphological processes under discussion do not differ from concatenative morphological processes in this respect. By adopting a transderivational approach, idiolectal variation is explained through a fixed hierarchy of markedness constraints in which certain constraints regarding different faithfulness relations are indexed (e.g., input-truncate, base-truncate and truncate-reduplicant relations). Some constraints on faithfulness relations are placed in a lower level in the hierarchy with respect to others, thus giving rise to different degrees of Emergence of the Unmarked effects. While the unmarked structure of the prosodic word and the syllable is explained by means of constraints grounded on the Prosodic Hierarchy, the unmarked structure of the the segment is accounted for by the use of constraints grounded on the particular Contrastive Hierarchy of the language.