One of the ribosome inactivating proteins (RIPs), beta-momorcharin, and a lectin were isolated from seeds of the bitter melon Momordica charantia (Family Cucurbitaceae) in accordance with published procedures. Both beta-momorcharin and M. charantia lectin were then subjected to amino acid sequencing. beta-momorcharin exhibited considerable homology in sequence to other Cucurbitaceae RIPs, and also to the A chains of abrin and ricin which are type II (double-chained) RIPs. The resemblance between alpha-momorcharin and other RIPs is closer than that between beta-momorcharins and other RIPs. M. charantia lectin manifested a certain extent of sequence similarity to beta-momorcharin and other RIPs, and some degree of homology in sequence to lectins from Cucurbita maxima, Cucurbita argyrosperma, Sambucus nigra and Ricinus Communis.