In the field of clinical psychiatry,cases of late-onset schizophrenia are often observed in the population of 40 years or older. Female patients seem to significantly predominate those diagnosed with late-onset schizophrenia. Generally, paranoid delusions of reference with family members, neighbors, and friends are observed as clinical features of such late-onset schizophrenia conditions. Medical treatment for such a condition is often effective and considered to improve the prognosis. The authors conducted clinical research at Jichi Medical University Hospital psychiatric ward involving 38 late-onset schizophrenia patients(7 males ; 31 females)diagnosed over the age of 40 using DSM-IV-TR diagnostic criteria.Subjects were selected from 316 schizophrenia patients (164 males ; 152 females)admitted to the hospital for schizophrenia treatment at some time during the 13 years from April 1,1993 to March 31,2006. Also,another 14 lateonset schizophrenia patients diagnosed over the age of 40 (1 male; 13 females), with additional investigation, were selected from 130 cases (50 males ; 80 females) treated in related facilities at some time during the 2 years from April 1, 2004 to March 31, 2006. The investigation revealed the following results : (1）Cases showing an onset after the age of 40 comprised 12% of the total population. Female cases comprised 20.4%, being significantly higher than that of male cases (4.3%). Within the psychiatric ward,cases showing an onset after 40 made up 10.8% of the total population. Female cases comprised 16.3%, being significantly higher than that of male cases (2.0%). (2）The paranoid type comprised 55.3% of the total population of late-onset cases, being significantly higher than in earlyonset cases younger than 40 years old. A total of 55.3% of late-onset cases also showed depressive symptoms, being significantly higher than in early-onset cases. (3）For lateonset, 55.3% of patients showed an introverted premorbid character, while 15.8% of patients exhibited an extroverted premorbid character. Regarding late-onset cases, the number of introverted premorbid character cases significantly lower than in early-onset cases diagnosed at 40 years or younger ; however, no significant difference was observed for the extroverted premorbid character. (4）A total of 65.8% of the population of late-onset cases were diagnosed as having psychosocial stresses as their cause. In addition, 36% of subjects with psychosocial stress recognition had experienced a sense of loss. Of these,66.6% of the loss experience involved separation from their family members. (5）Cases showing a successful recovery from schizophrenia comprised 55.3% of the total population. On the other hand, cases with an unsuccessful outcome were observed in 34.2% of the total population, accounting for a relatively large portion. A total of 30.8% of subjects with an unsuccessful outcome were unmarried at the time of onset,and made up 57.1% of the lateonset population. According to the results of this investigation, late-onset schizophrenia represents about 10% of the total cases, and female cases are significantly more common than male cases. For late-onset patients,subjects' self-functions were more developed compared to those of early-onset patients,so they did not seem to clearly show early-onset symptoms during a younger period. The late-onset type has a tendency to show a better rate of successful recovery; however, there are situations where the condition reverts toward the “disorganized type”, moving closer toward Kraepelin's early-onset disorganized schizophrenia.