Annual plasma levels of vitellogenin and sex steroids were investigated in relation to the gonadal development for understanding the endocrine control of reproduction in spotted flounder, Verasper variegatus. The plasma vitellogenin level was highest, 6.36 mg/ml, in November when vitellogenesis was most active. The level, thereafter, decreased to 3.81 mg/ml in December with the initiation of spawning. On the other hand, estradiol-17 $eta$ was highest, 2.7 ng/ml, in December, and rapidly decreased in January when spawning occurred. The decreased level of estradiol-17$eta$, around 0.2 ng/ml, remained unchanged until May. The profiles of plasma testosterone were similar to those of estradiol-17$eta$ in the fish, The plasma 17 $alpha$-hydroxyprogesterone level was relatively low throughout the spawning period, but increased slightly with the initiation of ovarian development, In males, the plasma testosterone and 11-ketotestosterone were highest in December when spermiation actively proceeded, but rapidly decreased during the spawning period (January).