The purpose of this paper is to study the Spanish spoken by first generation Colombians who have been living in the US for several years. Contact with English during long periods of time and the lack of first language use may cause a reduction in the Spanish proficiency of these individuals. Data collected in oral interviews revealed some changes at the lexical level that may be the first signs of L1 regression. A correlation between the time spent living in the US and the degree of change was found in these bilinguals. Some sociolinguistic factors, including contact with other Spanish speakers, contexts where both language are used, education and professional activities, are discussed in order to explain why some subjects have developed more changes than others in their native language.