Five selected lines of lentils (Lens esculenta Moench.) were used to determine percentages of natural crossing. First generation seed was classified into S1 and F1 groups after recessive fluorescent yellow cotyledonous maternal flowers were crossed naturally with pollen for dominant red cotyledonous flowers. Natural pollination between lines ranged from 0.01 to 0.08%. No F1 seed was produced on plants inside of wire screened cages although the cages included honeybees, air-borne pollen and maternal and paternal plants having alleles for yellow and red cotyledons, respectively. This indicates that neither honeybees nor air-borne pollen are major factors in natural cross pollinations. Seed yields from caged plants indicate that lentils are highly self-pollinated and need no agent to assist self-pollination.