Two size groups comprised stocks of the Japanese common squid (Todarodes pacificus) migrating in the Pacific Ocean off the Kuril Islands and eastern Kamchatka in June-September 2004. Small-sized squid were juveniles while large-sized animals were adults. Juveniles occurred in June-July, and had a mean dorsal mantle length (DML) of 76 mm. Mean DML of adult squid increased northeastward from 156 mm in June to 174 mm in July off the Kuril Islands, and 239 mm in September off eastern Kamchatka. In autumn, one individual was caught as far north as 55°N, which is the northernmost point of the species occurrence reported so far, and another one to the east of the Commander Islands, in the Bering Sea (Near Strait). All adult animals were immature and were intensively preying, mainly upon fish (primarily, Myctophidae), to a lesser extend crustaceans (primarily, Euphausiacea), and occasionally cephalopods (identified as conspecific juveniles). Our findings suggested that under certain conditions, particularly, in years of intensification of the Kuroshio Current and at high stock abundance, schools of the Japanese common squid may be widely distributed in the northwestern Pacific Ocean, and may even migrate as far to the north as the area adjacent to the Commander Islands during forage migrations.