In the early years of virtual reality in mental healthcare several reviews were published (Gregg and Tarrier 2007; G. Riva 2002; 2003; 2005). None of them mentions work done on virtual reality with psychotic disorders yet, though some early work was starting to get published around the same time. There are different psychotic disorders with each their own specified combination of symptom domains, symptom intensity and duration. Wood et al. (2011) suggest a dimensional staging of psychosis, ranging from psychotic-like experiences to severe persistent psychotic episodes. A large body of research is accumulating showing psychotic symptoms can be seen as a transdiagnostic and extended phenotype found in the general population (J. van Os and Reininghaus 2016). When psychotic experiences persist, transition to a psychotic disorder becomes a possibility. The main recognizable symptom domains of psychotic disorders are hallucinations and delusions. Hallucinations are perceptions a person experiences without a corresponding external stimulus. Hallucinations can occur for all five senses. Patients with a psychotic disorder for example often experience auditory hallucinations such as hearing voices. These voices can be commentary, give orders to the patient or call them names. Delusions are beliefs people have about the external reality which are strongly maintained despite strong evidence to the contrary or despite what almost everybody else (of a person’s culture or subculture) believes. The most common delusion found in psychotic disorders is the persecutory delusion (paranoia). People with a persecutory delusion feel others (known or unknown) spy on them, pursue them and threaten their safety (van der Gaag et al. 2012; Beck et al. 2009). Hallucinations and delusions often cause anxiety and make the patient avoid (social) situations, which can be treated with exposure therapy. Other symptom domains of psychotic disorders are negative symptoms and impaired cognition. Patients with negative symptoms experience an diminished emotional expression and avolition. Impaired cognition is about learning deficiencies, whether insufficiently thought or thwarted by deficits. For both negative symptoms and impaired cognition training can help patients learn to master new skills. There are some additional symptom domains in psychotic disorders, but these don’t play a part in virtual reality (yet). See Box 13.1 for an overview.@en