Previous research has found that schizophrenics with higher premorbid levels of social competence have better prognoses. These data have been used as support for a developmental theory of psychopathology, which has been applied to all psychiatric patients. This investigation, using 126 acute schizophrenics and 170 acute nonschizophrenic depressives tested the developmental theory on both schizophrenic and nonschizophrenic patients, using length of hospitalization as one index of prognosis. The data tend to support a developmental theory, which emphasizes social competence, when applied to schizophrenics alone. The evidence for a developmental theory, however, was negative when the theory was extended to nonschizophrenic patients. The data from the present study suggest that length of hospitalization is determined by severity of illness, which must be analyzed separately according to the type of disorder, using different criteria for each disorder.