Studies were conducted to determine the effect of resistant rice plants ( Oryza sativa L.) on the multiplication of the planthopper Sogatodes oryzicola (Muir). Plant resistance affected all phases of the life cycle of both nonvirulifcrous and viruliferous insects. Resistance reduced the number of eggs deposited and the number of nymphs hatched, lowered nymphal survival, prolonged the nymphal period, and reduced adult longevity. Because of more eggs deposited per day, greater egg fertility, and increased nymphal survival, susceptible plants supported about 10 to 12 times as many nymphs as did resistant plants. Of these, about 3 to 5 times as many nymphs became adults on susceptible rice as on resistant rice.