Spirantization is one of the most frequently studied phonological phenomena of Spanish (Barlow, Jessica A. 2003. The stop-spirant alternation in Spanish: Converging evidence for a fortition account. Southwest Journal of Linguistics 22. 51–86; Zampini, Mary. 1994. The role of native language transfer and task formality in the acquisition of Spanish spirantization. Hispania 77. 470–481; among others). For a majority of dialects, Spanish voiced plosives have been traditionally described as having a continuant and a non-continuant realization in complementary distribution (Navarro Tomás, Tomás. 1977. Manual de pronunciación española . 19th edn. Madrid: Consejo Superior de Investigaciones Científicas; Hualde, José Ignacio. 2005. The sounds of Spanish . Cambridge and New York: Cambridge University Press; among others). Yet, phonetic studies reveal a more complex picture consisting of a great deal of phonetic variability and gradience among continuant realizations (Carrasco, Patricio, José Ignacio Hualde and Miquel Simonet. 2012. Dialectal differences in Spanish voiced obstruent allophony: Costa Rican versus Iberian Spanish. Phonetica 69. 149–179; among others; Simonet, Miquel, José Ignacio Hualde and Mariana Nadeu. 2012. Lenition of/d/in spontaneous Spanish and Catalan. Paper presented at INTERSPEECH) which is not captured by existing generative accounts (Bakovic, Eric. 1997. Strong onsets and Spanish fortition. MIT Working Papers in Linguistics 23. 21–39; Harris, James W. 1984. La espirantización en castellano y la representación fonológica autosegmental. Estudis Gramaticals 1.149–67; Hualde, José Ignacio. 1989. Procesos consonánticos y estructuras geométricas en español. Lingüística 1.7–44; Kirchner, Robert. 2001. Phonological contrast and articulatory effort. In Linda Lombardi (ed.), Segmental phonology in Optimality Theory , 79–117. Cambridge: Cambridge University Press; among others). Furthermore, most analyses focus almost exclusively on the general distribution of spirantization, excluding other dialectal patterns (Amastae, Jon. 1995. Variable spirantization: Constraint weighting in three dialects. Hispanic Linguistics 6(7). 265–285; among others). The current proposal accounts for the phonetic variability and gradience evinced by phonetic studies, as well as dialectal variation in one optimality theoretic-analysis. Spirantization is explained as the result of effort reduction, rather than the result of assimilation (contra Harris, James W. 1984. La espirantización en castellano y la representación fonológica autosegmental. Estudis Gramaticals 1.149–67; Hualde, José Ignacio. 1989. Procesos consonánticos y estructuras geométricas en español. Lingüística 1.7–44, among others). Phonetic variability in the general dialects is argued to be related to the underlying representation: voiced obstruents are underspecified for continuancy both in the input and the output of the phonology, which explains gradience in implementation and responds to the need to avoid the marked configuration represented by a combination of voicing and maximal stricture found in voiced stops (Colina, Sonia. 2016. On onset clusters in Spanish: Voiced obstruent underspecification and /f/. In Rafael A. Núñez Cedeño (ed.), The syllable and stress: Studies in honor of James W. Harris . Boston, MA: Mouton de Gruyter). Dialectal variation stems from differences in the underlying representation and in the ranking of the constraints. The proposal is also able to explain variations on the two major dialectal patterns.