1. Urinary indole excretion of spot 14 appears to depend upon the presence of certain bacterial flora in the gut.2. When extraction of urine for chromatographic examination is carried out at pH 2.5, there appears to be no direct relationship between the appearance of indole 14 in the urine and the mental status classified as schizophrenia.3. From the dietary drug studies reported, we would conclude that the probable source of this indole derivative that was examined (spot 14) is from bacterial flora acting upon certain dietary substances in the gut.As Benjamin, Kety(38, 9), and others have pointed out, the area of psychiatric research to date which has a rather fruitless history is the search for definite and discrete biological abnormalities as presumed etiological factors in the development of the schizophrenias. In the main, when rigid controls have been maintained and research design has allowed for examination of all possibilities, an expected primary causal relationship generally fades into being a secondary manifestation of factors intrinsic to the diagnosis of schizophrenia, such as dietary differences, institutionalization, behavioral differences, and so forth. This has been well illustrated recently by the fate, for example, of interest in ceruloplasmin(28, 39) and in phenolic acid excretion (40). In the author's opinion, the particular indole compound we have studied, i.e., "spot 14," can be included in the above category.