Many primate populations exhibit forms of organization that are both complex and highly dynamic. A prototype of a general purpose primate population computer modelling system has been developed; this modelling system provides data structures and operators that facilitate computer representation of many static and dynamic features of primate population organization. In this system, primate group structures are represented by text strings known as key strings. A key string begins with a label or key character that identifies its population element type. The label character is followed by data fields contained between bounds marker characters. Nested key strings can be used to concisely represent many of the structural features of social groups in different primate species. Changes in group structures are accomplished by key string insertion, deletion and move operations. Models of structures and processes in island, rhesus monkey and hamadryas baboon populations built with this prototype modelling system are discussed. In these pilot applications, use of key string data structures and operators greatly simplifies many aspects of model construction.