Intoxication and withdrawal from a variety of central nervous system depressants and stimulants may induce hallucinations or delusions, which, when unaccompanied by insight, are the hallmarks of psychosis. A substance-induced psychosis may, in many instances, present as an organic psychosis or as an independent mental disorder (eg, schizophrenia), complicating diagnostic efforts. Ramifications of a misdiagnosed psychotic illness are potentially long-lasting and harmful to a patient. It is, therefore, crucial that health care providers be aware of the complex relationship between substance abuse, psychotic symptoms, and independent psychotic disorders. This report addresses substance-induced psychosis, by describing those psychotic symptoms most commonly associated with the abuse of specific drugs and alcohol, detailing useful diagnostic techniques and outlining treatment recommendations.