The first half of the 12th century was a decisive time for the first translations from Arabic into Latin. Among them, various figures stand out, notably two British, Adelard of Bath and Robert of Ketton. Their translations are wellknown, the former for Euclid, the latter especially for his Alcoran, even if he was first a specialist in astrological texts. The skills that these two men developed in Arabic allowed them to translate texts in particularly difficult fields: mathematics, astronomy, astrology, Islamology. By comparing extracts from the Latin translations of these two Englishmen with the Arabic original (Euclid and Ysagoga of Abū Ma’shar for Adelard; Alcoran and astronomical tables for Robert), the article identifies the principles of translation from Arabic followed by these two men, the difficulties they faced and how they sought to resolve them.