This study examined which body part labels children could (i) produce when the experimenter touched different locations on her own body, asking each time 'What's this?' and (ii) comprehend by touching the correct locations on their own bodies in response to the experimenter asking 'Where's the [body-part label]?'. Seventeen children aged between 26 and 41 months, tested in a repeated measures procedure, were presented with 50 different body part stimuli in 200 test trials per child. Overall, the children produced fewer body part labels than they could comprehend. The accuracy of children's responses depended on (i) the location or extent of each body part (facial and broad body features were better known; joints and features in or attached to broad body parts the least well known); (ii) the amount of sensory (but not motor) representation each body part has in the human cortex; and (iii) whether a body part was commonly named by caregivers. These results present a precise mapping of the body parts that young children are able to name and locate on their own bodies in response to body part names; they suggest several possible determinants of lexical-semantic body knowledge and add to the understanding of how it develops in childhood.