The concentrations of estrogenlike compounds in sediment were surveyed in Ise Bay and Ago Bay, which are typical of enclosed sea areas. Fourteen sediment samples were collected from the deepest part at the entrances to these bays. The examination of estrogenlike compounds was performed by a yeast screen assay developed by Professor J. P. Sumpter. The highest concentrations of estrogenlike compounds of sediment were found in the deepest part of Ise Bay (6.54 μg kg-1), and quantified as 17β-estradiol (E2) active equivalent. The concentration gradually decreased approaching the entrance of the bay from the deepest part of the bay. It was suggested that this decrease could be the result of biodegradation. The sediment assay samples were fractionated by high performance liquid chromatography and assayed to determine the chemical species of estrogenlike compounds. The detected estrogenlike compounds corresponded with E1 and E2, and were found in all of the samples. They are typical natural female hormones, and their origin is presumably domestic sewage and other wastewater containing feces and urine.