Oviposition activities of the larger black chafer(HolotTichia mOTosa Waterhouse) and Korean black chafer(H. diomphalia Bates) were examined in the laboratory and field from 1985 to 1990. In H. mOTosa and H. diomphalia, total durations of oviposition were 31.70$pm$17.33 days and 61.17$pm$23.15 days, numbers of days of actual oviposition were 9.00$pm$5.03 days and 22.33 $pm$11.72 days, total numbers of eggs laid laid per female were 23.43$pm$16.26 and 65.67$pm$37.97, and numbers of eggs laid per female per day were 2.60$pm$2.50 and 2.94$pm$2.34, under laboratory conditions. Difference of total numbers of eggs per female between both species seemed to be due mainly to numbers of days of actual oviposition. Oviposition period under laboratory conditions was considerably delayed behind that in the field in H. morosa but the two oviposition periods were almost overlapped in H. diomphalia. In the field, rates of gravid females of H. diomphalia were obviously higher than those of H. mOTosa, but numbers of eggs per gravid female were almost same in the two species, H. diomphalia adults did not show marked oviposition and feeding preference among several species of weed plants in the insect net chamber.