The authors happened to encounter a discordant schizophrenic case in one of uniovular twins. This patient is still yong so that we intend to follow up this case in the future, but for the time being we present this case as a discordant schizophrenia. 1. By the ovular examination this case has been verified as a uniovular case. 2. In the character test, namely, in Rorschach test and Uchida Kraepelin test, we found abnormalities not only in the patient but also in her twin-sister. This finding is noteworthy, so that it will not only help the ovular diagnosis but also suggests a possible danger of future nosogenesis. 3. By judging environmental differences between the twins, we have studies how these differences were related to the nosogenesis, and obtained the following data: (a) Both twins weighed only 1.5 Kg. at the birth, and the patient's entire body was paler than her twin-sister then. At the age of these both contrasted whooping-cough, but the patient was severer than her sister. It appears that from that time on the patient has the delicate constitution. (b) In the first year of her junior-high school days (13 years old) she received a trauma on the hiatus and she has been worrying ever since, believing she had her hymen broken. (c) As for the direct cause inducing the physiological and mental tension, cystitis which she suffered for one whole year when she was 15 years old may be pointed out. Cystitis seems to be an important factor in this case, because according to Henri Baruck in a cystitic case there are substances in Coli bacillus which are toxicant to the brain, and consequently there is a possibility of presenting a phenomenon like in schizophrenia reaction. These three factors seem to heve played an important role for the onset of schizophrenia in this case.