According to Erasmus' contemporaries, the Novum testamentum was his most important achievement. It is the translation of the New Testament from Greek to Latin. It replaced a thousand-year-old text by Hieronymus ("the Vulgate"). Erasmus removed the errors of the copyists and the translation could then be studied further. His notes, in which he expressed his opinion, often differed from the subject. He criticized various aspects of religious life, divorce, ...

As was usually the case, this work received both praise and criticism. Professors, religious and theologians were afraid that it would undermine the authority of the Vulgate and ultimately undermine the Catholic faith.