There is currently a great demand for child psychiatrists to be involved in child custody decision making. Lack of adequate training and limited criteria which deal with measurable psychological factors have made this a difficult problem for our field to meet. This paper describes a new assessment method, called the Parent-Child Interaction Test, for use by the child psychiatrist involved in child custody decisions. Experiences in its use by a family court are described. The historical development of custody criteria and an analysis of the working philosophy of a typical family court in custody cases is described, including criteria customarily considered and problems encountered in the decision-making process.