Cambridge was a well-established town and an important trade centre in the High and Late Medieval period (11th-16th century). Historical accounts and archaeological evidence indicate that the Late Medieval period was a tumultuous chapter in English history, with episodes of war, climate change, famine and plague. It is argued that the social and economic changes, particularly those associated with the Black Death of 1348-50, would have significantly affected food production and procurement in England and that dramatic population reduction may have resulted in changes in population replacement and diversity. However, it is not fully understood to what extent events in the Late Medieval period affected towns like Cambridge, and whether they were experienced universally across the local population. This thesis utilises contextualised isotope analysis of human and faunal skeletal remains from cemetery sites excavated from Cambridge and its hinterlands to investigate what life was like for the population living in the High and Late Medieval period. Isotope sampling focussed on High and Late Medieval skeletal remains, but to evaluate the scale of change across the longue durée, skeletal remains dating from the Neolithic to the Post-Medieval period were also sampled. A multi-tissue (bone, dentine, enamel) multi-isotope (δ13C, δ15N, δ18O, 87Sr/86Sr) approach was used to understand how diet and mobility varied at an intra- and inter-individual and population scale. Collagen from 246 faunal bones, 227 human tooth roots and 314 human ribs was analysed for δ13C and δ15N, carbonate from 295 tooth crowns was analysed for δ18O and δ13C, and 170 tooth enamel samples were analysed for 87Sr/86Sr. Successful results were combined with previously generated data from the area, totalling 252 faunal isotope results and 1174 human isotope results. The results of the isotope analysis have allowed for the characterisation of diet across multiple sites, indicating variation based on social status, religious beliefs and locality. Isotope analysis has identified a small number of individuals who were unlikely to have spent their childhood in Cambridge and may have migrated into the town. Potential localised, short-distance migration in women has also been identified. Most importantly, this thesis concludes that the data does not show conclusive temporal changes in the High and Later Medieval periods which could be linked to events in the 14th century. Some general temporal change in diet may be present, but this is likely to be linked to the increasing popularity of marine fish consumption following the ‘fish event horizon’.