Laboratory and field experiments in plant resistance to Lyyus lineolaris (Palisot de Beauvois) were carried out with bean, broccoli, and radish. The preferences among bean varieties shown by the adults for oviposition generally were different from the feeding and resting preferences of adults as well as the feeding and resting preferences of first-instar nymphs. The bean variety California Pink, on which the eggs had the highest viability, was also most preferred by first-instar nymphs. Varieties and sites preferred by the females for oviposition were not those where the eggs had the greatest chance of successful development. Thus, oviposition by the female and viability of eggs and nymphs were, at least partly, favored by a different set of conditions. The differences in preference and antibiosis within a botanical group (genus or family) appeared to be as great as or greater than the differences between such botanical groups. Laboratory experiments, supported by field observations, indicate that L. lineolaris was not able to breed with much success on any of the bean varieties used. Pronounced differences existed between the bean varieties, but Bountiful was most tolerant to attack by L. lineolaris. The bean varieties on which the greatest number of lygus nymphs were found were not the varieties on which the greatest number of leafhopper nymphs or aphid colonies were found. Thus the varieties most susceptible to L. lineolaris (e.g., California Pink) were not the most susceptible to other piercing insects. A population of L. lineolaris from alfalfa and one from a plant of the family Compositae exhibited oviposition and feeding and resting preferences for their respective plants. First-instar nymphs of these populations, reared on bean pods in the laboratory, showed the same preferences as did the parent populations; the differences were, therefore, due to genetic differences. The possibility of evolution of races of L. lineolaris according to the composition of the plant community where populations of the insect live may reduce the permanency of plant resistance to the insect.