The present paper aimed to make clear the spawning pattern of the red tilefish, Branchiostegus japonicus japonicus, by investigating the diameter distribution curves of their ovarian eggs. Samples of 273 ovaries were collected from the fish landed by bottom long-liners in the East China Sea during the period from April 1974 to March 1976. The results obtained were summarized as follows;
1) The ovaries were classified into eight types of maturation stage by analyzing the pattern of distribution curves of ovarian egg diameters.
2) Judging from the frequency distribution for each type in every month, it was concluded that the spawning of larger females (BL≥240mm) last for five months from June to October. But spawning in September was not so active.
3) In the case of smaller females (BL<240mm), it was estimated that most of them spawned in June, July and October, a few of them in only October and the remainder in June and July.