A very detailed and step-by-step explanation of a real translation commission for the Spanish-English translation of a medical article (negotiation, documentation through dictionaries, the authors and parallel texts on the Internet, selection of terms between synonyms, revision and relationship with journal's experts). Also an overview of the professional translator's profile: Language competence and technical knowledge, communicative and cultural competence; textual (genre-specific) competence; heuristic (documentation) competence; translational (techniques and avoidance of interference) competence; and professional competence (negotiation, rates, deadlines).