This study analyzes the Spanish of native speakers from Northern Mexico in order to ascertain the presence of the voiced labiodental fricative segment [v] when the sound is orthographically represented with the letter `v'. The study examines some of the internal and external factors that predict the labiodental fricative pronunciation of the letter `v'. This study is based on the theoretical framework of phonology as described by Piñeros (2009) and Hualde (2005). The study examined all instances in the data when a sound is written with the letter `v' to investigate if the sound is pronounced as the faithful voiced plosive bilabial allophone [b] of the phoneme /b/, the spirantized allophone [β], or the voiced labiodental fricative allophone [v]. Four speakers, a male and a female with an incomplete secondary education, and a male and a female with a graduate level education participated in the study. All participants were interviewed for one hour, read a word list, and read a paragraph provided by the researcher. The researcher coded the data using the phonetic analysis software Praat and all data were statistically analyzed using the multivariate software analysis program Goldvarb X in order to investigate the presence of the voiced labiodental fricative allophone [v] and predict what internal and external factors most influence its production. From this study it is obvious that the most influential factor favoring the realization of the labiodental fricative allophone [v] is orthography. When the phonetic segment was represented with the grapheme , the phonetic realization was more likely to be the labiodental fricative [v]. The level of education of the speaker and the formality of the stylistic setting were also determined to be influential factors. Speakers with a higher degree of education and stylistic settings with a higher degree of formality favored the realization of the labiodental fricative [v]. With regards to the internal factors, rather than external factors, a preceding phonological segment of a vowel or fricative dental [s] also favored the realization of the labiodental fricative [v].