Throughout his career, Roger Reynolds has studied perception and used this knowledge in an overt manner to shape many of his compositional decisions. Though this concern affects the ways that he works with many musical parameters, its influence is perhaps most clearly manifested in his global temporal designs. This article examines how he has approached form over the course of his career. Reynolds's initial compositional work from the early 1960s employed formal proportions that were derived from rows. Since 1970 Reynolds has used logarithmically expanding and contracting proportions to define sectional durations in his music to the near-exclusion of other designs. At the end of the 1980s and into the early 1990s, Reynolds began to look for sources of ‘alternative proportional authority’ such as chaos theory, while in more recent compositions his approach to formal design has been more variable.