The enclosure of open rangeland and its allocation to individuals or groups is a component of many African livestock development projects. In project after project, however, pastoralists have declined to fence or reallocate ownership of their land according to project specifications. It would now appear that the promise of a more efficient system of livestock production and range management is not, in itself, sufficient to induce pastoralists to adopt a fenced system of ranching. The present paper therefore examines some of the economic, social and legal factors which may discouraqe or encourage pastoralists to enclose common rangeland.