This brief review of the literature suggests that the existence of toxic methylated tryptamines is by no means as common as it should be if the methylation hypothesis of schizophrenia could have wide acceptance. Indeed, the occurrence of any of the postulated tertiary amines seems to grow rarer the more specific the methods used to search for them. It may be that only a very small percentage of persons suffering from schizophrenia are intoxicated by these amines, and therefore the presence of them during an exacerbation might point to a specific syndrome. It could also be that their presence in the CNS, plasma or urine is fleeting, and hence difficult to detect. In any event these findings along with those of other recent workers suggest that the early claims favoring the toxic indoleamine hypothesis would seem to be exaggerated. Certainly the detection of amines in urine and blood is dependent upon the sensitivity of the methods used. The critical threshold in this investigation was 4 ug/l and failed completely to detect their presence. Recently other methods capable of greater sensitivity have been used which can pick up these tertiary amines in urine and blood but their positive findings have failed to discriminate between healthy subjects and psychotic patients.