Using the sectioning of the otoliths of Pacific cod (Gadus macrocephalus), age determination was made for a total of 1, 076 individuals collected in adjacent regions of north Japan (off the southern coast of Hokkaido, the Musashi-Tai region, off Kinkasan, and the Matsumae-Kojima-Tai region) as well as off the Kamchatka Peninsula. The seasonal changes in percentages of otoliths with a translucent edge showed that the translucent part of the otolith was an annual growth ring formed during the autumn and winter. The change in monthly mean body lengths indicated that the body length of cod increased mainly between May and September. So we used samples collected during October and March for analysis of fish growth. The analysis of von Bertaranffy's curves revealed that there was little difference in growth rates in adjacent waters of north Japan, while it was significantly lower off the Kamchatka Peninsula.