This thesis is about the representation of herdsmen in bucolic poetry, mainly in Theocritus, with particular reference to the ways in which their roles in the poems and their different characteristics are affected by the 'pastoral hierarchy', that is the ranking or ordering of some types of herdsmen above others, placing cowherds on the top, shepherds in the middle and goatherds at the bottom.The hierarchy is certainly present in the characterisation of the herdsmen in Theocritus. It is normally goatherds who exhibit most explicitly the typical motifs of the new genre of bucolic poetry: the behaviour of lower-class people and their rusticity. They serve primarily for urban readers' derisive laughter. On the other hand, cowherds tend to function as retaining more traditional values in literature, to be depicted as more heroic or noble. The shepherds' character is set in some ways in the mid-point between those of the cowherds and goatherds: they can be elevated and associated with the nobility of the cowherds, or dragged down to a lowly characterisation similar to that of the goatherds.However, Theocritus occasionally changes the way the rule of the hierarchy is applied to his characters, so that his characters, especially the goatherds, have fascinatingly diverse features, such as Lycidas in Idyll 7, who holds a dual character, as a down-to-earth goatherd as well as the symbol of bucolic poetry itself.The different characteristics of herdsmen convey different aspects of the Idylls, such as the different levels of seriousness or playfulness in the different poems. Furthermore the goatherds' rusticity works to present pastoral as a radically new genre, clarifying its difference from traditional epic, whereas the cowherds' nobility functions to place the pastoral in the wider current of epic. Theocritean pastoral poetics are systematically made of these two sides, aepolic and bucolic.After Theocritus, the distinction between the herdsman-characters (cowherd, shepherd or goatherd) is often blurred and the hierarchy-based characterisation sometimes becomes less important. The post-Theocritean writers' various uses of the hierarchy and its occasional absence tell us of the development of the pastoral genre into diversity. Also, we find strong Theocritean influence in some significant descriptions of the goatherds as bucolic icons and rustics to be sympathised with.