 In this article, the principal concern is with the development of the Proof Interpretation within its original context of intuitionistic mathematics. Section 1 comments on terminology. Section 2 examines the basis of Brouwer’s conception of logic in his early writings. Section 3 presents his later refinements and also his views on Hilbert’s Program, Gödel’s incompleteness theorems, and the debate in the foundations of mathematics in the 1920s. Section 4 discusses formalizations of intuitionistic logic, which had begun even before the Proof Interpretation had been made explicit, and briefly looks at mathematical interpretations of the formalisms obtained. The explanation of the Proof Interpretation in Heyting’s writings from 1930 to 1956 is treated in section 5. The sensitivity of intuitionistic logic to the exact conception of mathematical construction was at the root of strong objections to parts of the Proof Interpretation that arose from within intuitionism. These are discussed in section 6. At the end, a short list is given of topics that will be added in future updates.