Explores problems in the measurement of evolving software systems. As these systems change through successive builds, the complexity characteristics of the individual modules that make up the system also change. A methodology is presented that extends the notion of software complexity domains across sequential builds. Changes to software systems are then measured on these attribute domains to provide leading indicators of potential problems introduced by the changes. Also, the notion of establishing a measurement baseline is presented. This permits the comparison of a sequence of successive software builds with one another. A specific software measurement example is presented using measurement data from the Space Shuttle Primary Avionics Software System.