Deterioration has been a part of the description and process of schizophrenia since Kraepelin. The underlying nature of these neurodynamic deficit processes remains unknown, but their clinical manifestations demonstrate somewhat predictable patterns of expression and progression. Symptomatically, strong affects and positive psychotic symptoms in the early course become less conspicuous with time and are replaced by more thought disorder, disorganized behavior, negative symptoms and deficit cognitive states. Subtypes, when unstable, drift from paranoid to disorganized and undifferentiated and from non-deficit to deficit. Longitudinal data from the schizophrenia sample of the Chestnut Lodge follow-up study illustrate some of these patterns. While the data remain heterogeneous, it is likely these deficit processes begin some time before the first manifest signs and symptoms of illness in the prodromal phase and are time limited, diminishing in activity at or shortly after onset in the majority of cases. Currently these processes appear irreversible but anecdotal experience with treatment in the very early phases of schizophrenia suggests that brain plasticity may be retained and that efforts at preventing deterioration should become a focus of active scientific clinical research.