For successful prosecution, investigative interviews with child sexual abuse victims need to establish the nature of the alleged offence by determining the body parts that were involved. To date, however, there has been a paucity of research on the extent to which children clearly identify sexual body parts in interviews and how they respond to interviewers’ attempts to clarify ambiguous terms. The present study sought to explore children’s use of sexual body part terms in field interviews, and their responses to questions aimed at clarifying ambiguous terms. Analyses were conducted on 161 transcripts of field interviews with children aged 4–17 years old, coding for the content of interviewers’ questions and of children’s responses. Results revealed that many children, even some in their late teens, struggled to provide clear terms for their sexual body parts, either initially, or when asked to provide an alternate term. Questions about body part location or function tended to elicit content appropriate responses in children, irrespective of age. The study discusses the capacity (or willingness) of children to provide clear body part terms in witness interviews and the utility of particular questions. The findings imply a need for caution when following up on the meaning of terms or asking particular clarifying questions, and highlight the importance of childhood education around body parts.