OBJECTIVE: The authors explore the antecedents, symptom progression, and long-term outcome of patients diagnosed as having the deficit syndrome, a putative domain of psychopathology and subtype of schizophrenia defined by Carpenter's group. METHOD: Patients from the Chestnut Lodge Follow-Up Study were retrospectively rediagnosed as having deficit (N = 46) or nondeficit (N = 141) forms of schizophrenia by using the criteria of Carpenter's group. Patients with deficit and nondeficit forms of schizophrenia were compared in relation to symptom progression between first and index admission, natural history and course of illness, and long-term outcome assessed at follow-up a mean of 19 years after index admission. RESULTS: 1) Significantly fewer patients with the deficit form of schizophrenia were married before illness onset, but few other differences between patients with deficit and nondeficit schizophrenia emerged. 2) Illness onset was often insidious for patients with the deficit syndrome; once established, the illness was nearly always continuous with few remissions, and its course appeared unreactive to life events. 3) Negative symptoms among patients with the deficit syndrome were often present at illness onset and progressed in severity over the first 5 years of illness; thought disorder and bizarre behavior also increased in severity over time. 4) Once established, the deficit syndrome was highly stable. 5) The deficit syndrome was associated with a very high risk of poor outcome and long-term disability. 6) None of the patients with the deficit syndrome were known to have committed suicide. CONCLUSIONS: The data support the validity of the deficit syndrome as a subtype of schizophrenia with a relatively distinct natural history.