• The clinical course, body weight, biological measurements, and responses to neuroleptic agents were examined in 92 chronic schizophrenics over a period of ten years. The individual occurrence of periodic exacerbations, shifts in symptoms, changes in drug responses, unusual fluctuations in body weight, and transient biological abnormalities led me to conclude that schizophrenia is characterized by an independent variability of clinical and biological features. This variability indicates that schizophrenia is a disease of regulation.