The D0 experiment has used the 'Structured Analysis/Structured Design' (SA/SD) methodology in its software development for the past year. The data flow diagrams and data dictionaries of structured analysis were the primary tools used in development of an ideal model of the D0 software system. These and the structure charts developed during the design phase form the basic documentation of the system. Real-time structured development techniques, e.g. state transition diagrams, are employed to describe control functions in some areas, e.g. in the calibration software. The SA/SD methodology has proven to be valuable in the formulation of ideas and in communication between software developers. The methodology and its application to D0 software are described and the benefits and problems are assessed. Problems finding adequate software tools for the VAX environment are discussed and a data dictionary manager developed by D0 using DEC RDB is described.