Family therapists, seen as emphasizing interventions leading to change in family structure and in sequences of behaviour, have been searching for an integrated concept which transactional systems theory seems to offer. It takes into account small group theory, social role theory, communications theory, and general system theory, which are linked to psychic, somatic, socio-cultural, politico-economic, and ecological factors. This idea of interlinked, open systems which influence each other is used as a viewpoint for examining the frontiers of child psychiatry. Adult patients often have children who are affected by their parents’ treatment, and child psychiatrists often intervene with adults. Similarly, the boundaries between psychiatry and the paramedical professions have grown less distinct as we have become aware of more elements to assess in each case, and as the number of therapeutic techniques and possible interventions increase. The problem of defining child psychiatry is discussed, as is psychiatric training, in terms of the difficulty in integrating the many theoretical and practical levels.