Interviewing can provide unique opportunities for professionals to gain some understanding of the child's subjective experience, where other means of data collection are inappropriate and other sources of data are less valid. This article is concerned with the principles and practicalities of interviewing children for the purposes of health-related research. It draws on the knowledge gained from three decades of research involving interviewing young people in many contexts, including health care, social welfare and child protection. A conceptual framework is presented to illustrate the interactive and iterative processes that occur between interviewer and interviewee, and the pivotal importance of context in shaping any interaction. The influences of the young person's linguistic, cognitive and social skills are discussed. The effects of the gender and ethnicity of both the researcher and the researched are considered in relation to the conduct of the interview, and the influence of adult biases and perspectives on the evaluation and interpretation of data is explored.