The aim of this study is to observe the adulticidal activity of five essential oils against the mosquito Culex pipiens quinquefasciatus. Fumigating adulticidal activity was investigated by airtight fumigation in conical flasks. The result showed that the toxic effect of the five essential oils varied with the period of fumigation. Rutaceae oil was the most toxic of the five. Carvacryl oil had the shortest adulticidal time (6.087 min). The chemical components of rutaceae oil were analyzed by GC/MS. The major components were α-citral (33.50%) and citral (35.77%). Citral showed marked adulticidal activity in a short-term fumigation. All five essential oils had considerable adulticidal effects on Cx. pipiens quinquefasciatus. © Pesticide Science Society of Japan