This paper describes research carried out through electronic surveys of three groups of translators working in different areas of expertise (legal, medical and technical) that aimed to discover their socio-professional profile, their opinions both on corpora and other documentary sources, and the use they make of them. Certain characteristic features emerged from the analysis of data on the three population groups, regarding years of experience, documentary sources used and most usual clients. For example, even if legal translators seem more satisfied with the documentary sources available, medical translators never use translation memories, and technical translators often refer to thesauri. In any event, regardless of their area of activity, most subjects feel the need for a specialized corpus combining formal, terminological-lexical, macrostructural and conceptual aspects, as well as contextual information. That is the reason why the GENTT 3.0 Corpus is believed to meet the expectations and needs of professional translators.