The concentrations of organotin (OT) compounds were surveyed in four coastal areas of Japan (the Port of Osaka, Maizuru Bay, Otsuchi Bay and Tanabe Bay). Tributyltin (TBT) concentrations in water and sediment from the Port of Osaka were higher in a marina and a mooring for small- and medium-hull vessels than the other areas. Some alternative compounds were detected in the Port of Osaka; especially, diuron concentration was the highest. OTs concentrations in Maizuru Bay are lower among those coastal areas in Japan. Diuron and Irgarol 1051 were detected in the sediment from Maizuru Bay. Concentrations of Diuron and Irgarol 1051 in the vicinity of a shipyard and a small fishing port from Otsuchi Bay were dramatically high in comparison with the other sites. Copper pyrithione and Dichlofluanid in addition to Diuron and Irgarol 1051 were also detected in sediment of the area of a small fishing port from Otsuchi Bay. OTs concentration in Tanabe Bay is the highest among the coastal areas in Japan and the concentrations of alternative compounds were lower than those of OT compounds. OTs concentrations were surveyed in the deep sea environment. In the sediment core of 0-30.5 cm from Suruga Bay, the BTs and PTs concentrations were constant between 0-15 cm and subsequently the concentration of these compounds increased, showing the peak between 18-19 cm. After the peak, TBT and TPT concentrations decreased. In Tosa Bay, BTs concentrations decreased with the depth, suggesting the spread of OTs contamination from coastal waters. OTs and alternative biocides were detected even in the sediment and organisms from Nankai Trough (4000 m in depth). The highest concentration of TBT in Thailand was detected at an industrial area with shipyards. On the other hand, TPT was not detected in the sediment. The concentrations of TBT in some mussel samples from Thailand were higher than TARL (Tolerable average residue levels). Among alternative biocides, Diuron was only detected. Concerning the marine mammals, the concentrations of BTs were high in the order of whales>dugongs>dolphins and the concentration of PTs in whales was higher than that in dolphins and dugongs. The concentrations of MBT, DBT and TBT in sediment from the coastal water of Peninsular Malaysia were measured. TBT concentrations in Johor Strait were higher than those in other sites in Peninsular Malaysia. Although TBT concentrations in sediment from Vietnam were low, Sea Nine 211 concentrations were high. Thus, the contamination of antifouling biocides has expanded widely from the coastal area to deep-sea environments in Japan and Southeast Asia. The necessity of the continuous research is therefore suggested.Proceedings of the Horiba International Conference "New Direction of Ocean Research in the Western Pacific" : Past, Present and Future of UNESCO/IOC/WESTPAC Activity for 50 years and the JSPS Project "Coastal Marine Science"Section II: Historical Review of Coastal Research in Southeast Asia