In order to find a clue to the causes of insect resistance in rice varieties, feeding habits and honeydew components of the green rice leafhopper, Nephotettix cincticeps UHLER, were compared for resistant and susceptible varieties. The leafhopper excreted as much honeydew on resistant varieties as on susceptible varieties. The honeydew form resistant varieties contained a small amount of sugars, whereas the honeydew from susceptible varieties contained 0.36% of sugars as glucose which was composed of four kinds of sugars. The results suggested that the leafhopper was unable to suck the phloem sap of resistant varieties. Stylet sheaths were terminated both in xylem and in sieve tubes on resistant varieties. The proportion of stylet sheaths terminated in the sieve tube was significantly smaller for resistant varieties, although the leafhopper made more probing punctures, 2.4-3.4 times as many on resistant varieties as on the susceptible variety. Thus, the number of stylet sheaths terminated in the sieve tube per unit time became similar for resistant and susceptible varieties. It is reasonable to conclude that the antibiosis and non-preference of resistant varieties are respondible for the inability of the leafhopper to suck the phloem sap, even when the insect inserts its stylet into the sieve tube.