Abstract This paper reports δ 13C and δ 15N values for human and animal skeletal remains from the Middle Horizon (AD 550–1000) site of Conchopata in the Peruvian highlands. The data indicate that maize was the dietary staple for both humans and the majority of animals at this urban site. Camelids at the site segregated into two groups according to δ 13C values, reflecting two distinct animal management strategies. Human infants were found to have elevated δ 15N values, reflecting the trophic level effect of breastfeeding. No sex based differences in diet were observed.