Abstract: Ten lectins from different sources were screened for cytotoxic activity against Acanthamoeba sp. (a keratitis-causing amoeba) and Tetrahymena pyriformis (a ciliate). Lectins from Schefflera odorata (“lima-lima” plant) [molecular weight = 271 kDa], Swietenia macrophylla (large leaf mahogany) [molecular weight = 295 kDa] and Lenzites sp. (a mushroom) [molecular weight = 184 kDa] were found to possess high cytotoxic activity against the test organisms. These results indicate that lectins may be further exploited as potential chemotherapeutics against certain parasitic diseases.