The use of virtual reality is not new in the treatment of psychological stress and anxiety disorders: virtual worlds are used to facilitate the activation of the stressful events during the exposure therapy. However, during the therapy, the virtual worlds are new and distinct realms, separate from the real-life emotions and behaviors. In fact, the patient’s behavior in the virtual world has no direct effects on his/her real-life experience, and emotions and problems experienced by the patient in the real world are not directly addressed in the virtual exposure. In this paper we present the INTERSTRESS project, a new technological paradigm for the treatment of psychological stress in soldiers, based on interreality. The main feature of interreality is a twofold link between the virtual and the real worlds: (a) behavior in the physical world influences the experience in the virtual one; (b) behavior in the virtual world influences the experience in the real one. This is achieved through 3D shared virtual worlds; biosensors and activity sensors (from the real to the virtual world); and personal digital assistants and/or mobile phones (from the virtual world to the real one). We will describe the different technologies involved in the interreality approach and the clinical rationale of the protocol. To illustrate the concept of interreality in practice, a clinical scenario regarding a soldier affected by acute psychological stress will be also presented and discussed.