This article emphasizes the growing need for good technical communication in application program development, and relates the usability of program documentation to the productivity of computer systems. It describes in detail the process involved and the human thinking that must accompany the generation of high quality computer user documentation. The methodology described in this paper has been exercised by the author on two major interactive IBM application programs. However, the methodology should not be interpreted as an IBM discipline, and views expressed in this paper are those of the author.