The objective of the work presented in this thesis was to develop valid, reliable and feasible indicators for the on-farm assessment of sheep welfare. In the absence of a reference test for animal welfare assessment, the welfare indicators in this thesis were developed within the Farm Animal Welfare Council( FAWC) Five Freedoms framework. A scientific literature review and the consensus opinion of a panel of experts were used to judge the face and consensual validity of a selection of indicators of sheep welfare. Experts identified 193 current on-farm welfare issues for sheep and subsequently suggested a range of animal- (n = 26), resource-( n = 13) and management-based indicators( n = 22) in order to assess the on-farm welfare of adult sheep( > 1 year-old), growing lambs (> 6 weeks -