The naturally occurring indole derivatives in mung bean (Phaseolus vidissinus) sprouts were investigated by means of paper and thin layer chromatographic techniques. The results can be summerized as follows: 1. The mung bean sprouts are richer in free tryptophan than other plant species. 2. Indole ethanol and indole lactic acid were identified. 3. The content of indole ethanol was more than that of indole acetic acid. This result appeared to support the idea that indole ethanol is the storage product of indole acetic acid.