The egg production rate (EPR) of the lobate ctenophore Bolinopsis mikado was measured in summer, fall, and winter using field-collected animals whose total lengths (TL) ranged from 17 mm to 73 mm. The TL of spawning B. mikado ranged from 22 mm to 73 mm, indicating that B. mikado matures at ca. 20 mm TL. Because the percentage of spawning individuals to the total ranged from 50% to 100%, B. mikado probably spawned intermittently or daily in Tokyo Bay. Spawning individuals were found even in December and January. Bolinopsis mikado seemed to reproduce continuously in Tokyo Bay throughout the year. A multiple regression analysis between the EPR and ctenophore body size and water temperature suggested that 21.5% of EPR can be explained by these variables. The EPR increased linearly with ctenophore size, i.e. the wet-weight specific EPR (EPR*) was independent of the body size. The relationship between the EPR* and water temperature was equivalent to a Q₁₀ value of 4.7, and was considerably higher than that of the respiration, predation, and growth rates, which may lead to quick population growth and mass occurrence of B. mikado during summer and fall in coastal waters.