This account of the great variety of stops in the world's languages shows that, apart from their place of articulation, these sounds can be described principally in terms of the activities that occur at three phases: onset, closure, and release. Other potentially contrastive features discussed include length, and the use of the glottalic airstream mechanism (other airstream mechanisms are not considered here). Phonologically only two phases--closure and release--are exploited; independent distinctions of features such as phonation type or articulatory manner cannot be found in the onset phase. We examine the combinatorial possibilities of the features that are used and discuss implications for phonological feature systems.