Seclusion is a common treatment method in psychiatry. However, there are contradictory reports about the effects of the sensory deprivation involved in seclusion on the distortions of perceptions seen in some psychiatric patients. This descriptive study explored the seclusion experiences of seriously ill psychiatric patients; described the hallucinatory experiences of these patients during seclusion; and examined the relationship between hallucinations and sensory stimulation, as reflected in staff visits and length of time secluded. Consenting adult male and female psychiatric inpatients (n = 25), with DSM III-R diagnoses of schizophrenia or schizoaffective disorder were interviewed within 5 days after a seclusion experience, using a modification of Richardson's structured interview guide. Approximately half of the patients hallucinated in seclusion; however, 70% of these had also hallucinated before seclusion. There were no significant relationships between hallucinating in seclusion and frequency of staff visits or length of time secluded; however, patients who hallucinated received significantly more "as needed" (PRN) medications and had more therapeutic visits than patients who did not hallucinate.