Recent reports suggest some utility for famotidine, a histamine type 2 (H2) antagonist, in the treatment of schizophrenia. The current report describes a treatment-resistant patient with chronic undifferentiated schizophrenia whose most dramatic symptomatic improvements were temporarily related to the open-label addition of famotidine (40-100 mg/day) to conventional neuroleptic treatment (molindone 150-200 mg/day) over the course of approximately 10 months. During one 2-week interval, his symptoms were controlled with famotidine (40 mg/day) alone. The case suggests that some adjuvant efficacy exists for famotidine in at least some patients with schizophrenia. Placebo-controlled trials are needed to more fully evaluate the utility of famotidine in the treatment of schizophrenia.