This study investigates, from an articulatory point of view, the extent to which the different nasalization processes in Brazilian Portuguese (BP) - phonemic, allophonic and coarticulatory - are the result of phonological, language specific rules or a purely phonetic transitional phenomenon between an oral vowel and a nasal consonant. The study revealed that the magnitude of the velic gestures is similar in phonemic and in allophonic nasalization, which suggests that both processes are the result of the application of phonological nasalization rules in BP. On the other hand, in coarticulatory nasalization the degree of velic opening reached during the vowel is smaller, suggesting that in this case we have a purely transitional, coarticulatory phenomenon.