Two ovitraps filled with rainwater were placed on the campus of Taegu National University of Education and newly-laid egg masses were collected to investigate the oviposition activity of Culex pipiens molestus and Culex pipiens pallens and the characteristics of egg masses during July-October, 1996 and April-June, 1997. The results are as follows: C. p. molestus and C. p. pallens constituted 15.4% and 82.4%, respectively, among the egg masses collected. Many of autogenous C. p. molestus living in the underground habitat were active on the aboveground. The egg mass of C. p. molestus was collected mainly in July and September; that of C. p. pallens, in July and August. The mean number of eggs per egg mass was 118.2$pm$10.6 (mean$pm$SE) in C. p. molestus and 154.5$pm$4.4 in C. p. pallens. The former showed a significant increase over the mean of 76.7$pm$0.9 (Sohn, 1993), indicating that many of autogenous C. p. molestus oviposited by bloodsucking on the aboveground. The fertilization rate of the egg mass was 100% in both species; egg hatchability in the egg mass of C. p. molestus and C. p. pallens was high at 89.9$pm$3.7% and 93.0$pm$1.1 ％, respectively. The monthly egg hatchability in the egg mass of C. p. molestus was high in July (97.4%) and September (96.8%) and low in August (83.8 %); that of C. p. pallens was high in June through September (over 94%) and low in October (59.8%).