Complete amino acid sequences of karasurin-B and karasurin-C purified from root tubers of Trichosanthes kirilowii MAXIM. var. japonica KITAMURA (Cucurbitaceae) were determined. Karasurin-B consists of 247 amino acid residues with a calculated molecular weight of 27214 Da and karasurin-C of 249 amino acid residues with a calculated molecular weight of 27401 Da. Their amino acid sequences are quite similar to that of karasurin-A, a major basic protein from the same root tubers, but the pI values are slightly different amoung them. All karasurins strongly inhibited in vitro translation in the rabbit reticulocyte system. The amino acid sequences of karasurins were compared with those of the ribosome-inactivating proteins (RIPs) from nine different species by UPGMA method, and the RIPs from Cucurbitaceae plants phylogenetically formed one cluster clearly distiguishable from those of other origin.