Having held competitive multi-party elections on a regular basis since 1965 Botswana presents a unique case in the African context for the study of the evolution of the party system over a considerable period of time. During this period the socio-economic conditions in which the party system operates has been transformed largely as a result of spectacular economic growth. This article seeks to explain how and why the party system of Botswana has changed during this period and also why it has changed relatively slowly. It is argued that Botswana has experienced a continuous movement away from a dominant-party system. A combination of factors relating to both human agency and socio-economic structure provide the basis of the explanation for change.