A one step rapid and simple purification procedure for trichosanthin, a type 1 ribosome inactivating protein, from root tubers of Trichosanthes kirilowii has been developed using cation-exchange perfusion chromatography. The identity of the protein has been confirmed by its size, immunoreactivity, and sequence information. Yields of 0.16% of electrophoretically pure trichosanthin from dried root tuber have been achieved with a single 10-min chromatographic step giving the ability to purify gram quantities of trichosanthin in 1 day.