A fundamental problem in phonological theory is the fact that processes often operate on consistent subsets of the distinctive features within a segment, like the features that characterize place of articulation. Recent research has responded to this problem by proposing a hierarchical organization of the features into functionally related classes, grouped under nodes of a tree structure. This ‘geometry’ resembles earlier theories that accomplish the same thing with multivalued features. This article reviews and expands the evidence for feature geometry. Within the segment, it is argued, the major dichotomy is between a Laryngeal node and a Place node. The manners of articulation – sonority, consonantality, nasality, and continuance – inhere in the segment itself rather than any of its subsidiary parts. Within the Place node, the division is into major articulators, each with its own subordinate features. Evidence is drawn from processes of assimilation and debuccalization and from the assimilatory and dissimilatory effects of the Obligatory Contour Pr