The objective of the present study is to show the process of organization of a bilingual collocations glossary (Portuguese-English) in the medical field, emphasizing the importance of knowing the correct terminology for translating, revising and teaching English. Theoretical and methodological support was provided by Corpus Linguistics, which emphasizes the importance of empirical data analyses and views language as a probabilistic system. Besides, it allows the investigation of large quantity of data through computational tools, e.g. WordSmith Tools. Two corpora, one in Portuguese and one in English, with approximately 85.000 words each were compiled. The results indicated that the use of corpus in inverted translation tasks is very important, especially when it deals with collocations of a specific field. We concluded that although the organization of a glossary is not an easy task and requires great care and dedication in all its steps, it is very useful for those who work with the English language.