The development of a new frontier for research and early intervention in psychotic disorders is highly dependent on the construction of synergistic clinical infrastructures. This has catalyzed great progress in the recognition, enhanced treatment, and study of first episode psychosis, and the task is even more challenging when the boundaries are extended to include the earliest clinical phase of illness, the prodromal or prepsychotic phase. This article describes the conceptual and practical building blocks for the construction of service models for intervention in the postonset clinical phase prior to the attainment of current diagnostic thresholds. This is best regarded as indicated prevention, a form of very early secondary prevention, which involves a blend of immediate clinical care combined with research-oriented preventive intervention. The experience of the Personal Assessment and Crisis Evaluation (PACE) Clinic in Melbourne across several stages of growth is described and contrasted with that of several emerging centers in Europe and North America. The progress to date, the lessons learned, and the unresolved challenges and opportunities are detailed. It is concluded that service models can be developed that are acceptable and helpful to young people and their families, and that create a unique environment for the study of the transition to frank psychotic disorder. The ultimate clinical utility and general safety of this approach and the range of effective treatments remain unclear, and will be determined by more extensive research. Such research must be conducted in a logical and rigorous manner with the best designs possible, sensitive to input from consumers and caregivers and to ethical considerations.