Concerning cause of the SMON, there are many opinions from epidemiological, clinical and pathological points of view, and yet no distinct cause has been found. In order to clarify the cause by epidemiological procedure, we tried to investigate the relation between chinoform administration and the SMON from the data of the clinical cards in a hospital. 1) The average amount of chinoform administered during the whole course of treatment to the SMON patients in Y district was about 281g. and that in all Jaqan was about 147g, while the average amount calculated from the data of Berggren and others was 863g. 2) The average amount of chinoform administered to SMON patients until nervous symptom appeared was 69g in Y district, and that was 52g in all Japan. 3) The SMON patients of multiple occurrences in a family were all administered chinoform. The eight of nine SMON patients of multiple occurrences in a hospital were administered chinoform. 4) The tendency was recognized that SMON patients who received appendectomy had stayed for rather longer duration in a hospital and the SMON patients who did not receive appendectomy had relatively benign progress. The tendency was also recognized that the amount of chinoform administered to the SMON patients who received appendectomy was a little larger than that administered to the SMON patients who did not receive appendectomy.