GLC provides the easiest and most rapid way of determination of these compounds in various plant materials, and it can be expected to play a large role in the future for identification of hitherto unknown structures, especially since only small samples of the original material are needed. Work is at present on the way in our laboratory, where parts such as root, leaf, bark of reputed psychoactive plants are investigated. An example of this is the rapid identification of harmine derivatives in species of Banisteriopsis. In my opinion, the experience gained by GLC analysis of indoles in plants will provide us with a very good background for future work with other sources of tryptamines such as urine and brain. For current analytical gas chromatography columns, only a very small volume may be applied (1-10 microliter) ; hence, high indole concentrations must be achieved for suitable detection. This is in contrast to spectrophotofluorometric techniques whereby indoles may be detected at the 0.1 microg level in 1 ml of fluid. However, in situations where high concentrations can be obtained, gas liquid chromatography permits not only qualitative resolution, but quantitative estimation as well. A final outstanding feature which I hope has been well documented is the ability for gas liquid chromatography to resolve closely related compounds. Along with the development of better extraction and concentration procedures an increasing sensitivity of the gas chromatographic systems may be expected.