The cytotoxic plant lectins from P. sativum have been used to select new lectin-resistant mutants from Chinese hamster ovary (CHO) cells. Two novel phenotypes that behave recessively but fall into the same complementation group have been termed Lec13 and Lec13A. Both of these mutant types are phenotypically reverted to pea lectin sensitivity following growth in L-fucose. In contrast, two other unique phenotypes behave dominantly in somatic cell hybrids and maintain their pea lectin-resistance in the presence of L-fucose. They have been termed LEC14 and LEC18, respectively. The lectin-resistance and complementation properties of the four new mutant types suggest that they define three different glycosylation genes of the CHO genome.