Dioxin-like and estrogenic activities were measured in a sediment core collected from Tokyo Bay using in vitro bioassays after fractionating sediment extracts into three fractions by florisil column chromatography. Target analytes including polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), polycyclic aromatic hydrocarbons (PAHs) and nonylphenol (NP) were measured by gas chromatography-mass spectrometry (GC-MS) or high performance liquid chromatography (HPLC) techniques. NP concentrations were greater in surface sediments (0 to 12 cm) than those in sub-surface (12-30 cm). The maximum observed PCN concentration was 5 ng/g, whereas that of PCBs was 300 ng/g. Concentrations of PCBs in fraction 1 (F1) were not high enough to induce significant luciferase activities in H4IIE-luc cells. Significant dioxin-like activities were found in fractions 2 (F2) and 3 (F3). PAH concentrations were correlated with dioxin-like activities measured in F2. Compounds that contribute to the dioxin-like activities in F3 were not identified yet. Significant estrogenic activities were observed in F2 samples, which may be related to the presence of certain estrogenic PAHs. F3 samples were cytotoxic to MCF-7 cells and therefore their estrogenic potential could not be estimated.