OBJECTIVE: This study examined which characteristics of hallucinations are most likely to change after inpatient treatment. METHOD: Fifty hallucinating psychiatric inpatients were given semistructured interviews shortly after admission and again shortly before discharge to elicit detailed descriptions of 12 characteristics of hallucinations. RESULTS: Twenty-eight (56%) of the 50 patients continued to report hallucinations after inpatient treatment. Posttreatment hallucinations differed significantly from pretreatment hallucinations in that they were less frequent, less intense, and less likely to prompt overt behavioral responses. Other characteristics of hallucinations remained relatively stable. CONCLUSIONS: Even when treatment does not eliminate hallucinations, it may alter them significantly. Outcome criteria that consider only the presence or absence of hallucinations may miss important changes in the nature of the symptom. This demonstrates that there is no simple "on-off switch" for hallucinations and supports multifactorial theories of the etiology of hallucinations.Abstract Teaser