This thesis was based upon an interdisciplinary research project “Information and Communication Technologies” (ICT‘s) for Language Learning and Edutainment in Internet a , FONDEF D05I - 10243), where we could apply our knowledge about Error Analysis and focus our attention on five of the phonological processes that occur when Chilean - Spanish native speakers from Santiago, attempt to pronounce words in English. We noticed how important the teaching of phonetics is when learning a foreign language, English in this case and how it has been treated by the current trends in teaching foreign languages, which leaves it aside or ignores it. According to different studies, ¯formal phonological instruction results in improved student accuracy of pronunciation. For this reason, we thought our participation in the project mentioned above as a crucial contribution to the development of a software for secondary - school students to practise the English they learn in the classroom. We were aware of the fact that we could not demand much from their pronunciation, but we also knew that it was important to emphasise the allophonic differences that many times change the meaning of a word, so we agreed on the criteria used to work on the samples that we got from the project. From here, we decided to start our own research on the words recorded by a certain group of speakers. According to theories on Error Analysis (EA), the errors made by the speakers are considered to be a useful device in the process of Second Language Acquisition, and by doing our research, we will attempt to provide examples of these errors and how they affect the intelligibility of a word. At the same time, and as a way to complement our investigation, we considered some aspects of Interlanguage that are rarely taken into account when dealing with SLA and phonetics, mainly the psycholinguistic processes which help the development of the learners‘ interlanguage. As it was said before, we will want to highlight the importance of the allophonic features of words uttered by native Chilean - Spanish speakers and the possible errors they will make by doing so.