Hunayn ibn Ishaq is one of the most important translators of scientific and medical texts in the 'abbasid era. He played a fundamental role in the transmission of Greek medical science to the Arab world, because of his deep knowledge of the Syriac, Arabic and Persian languages. He translated about 300 texts, especially medical ones, and he founded a school in which many disciples were instructed in the art of translation, like his son Ishaq and his nephew Hubays. Hunayn composed a lexicon of scientific terminology, using a new method of translation which represents his great innovation. Key words: Hunayn - Greek medicine - Arabic medicine - Translations