Distribution of dioxins (PCDDs, PCDFs, and Co-PCBs) in atmospheric deposition, soils, and bottom sediments of rivers and coastal sea were examined in Hiroshima prefecture, Japan during 1998-1999. The monthly concentrations of PCDDs/DFs in atmospheric deposition (rain and dry deposition together) were 1.3-3.3 pg-TEQ/L and the monthly depositions were 4.1-20 pg TEQ/m2/day in Fukuyama during April to September in 1999. PCDDs/DFs concentrationsin soils were 4.9-34,1.2-2.5, 1.1-6700 and 77-86 pg-TEQ/dry g at Mt. Gokurakuji in Hatsukaichi, at a forest in Souryou Town, at industrial incinerators in Fukuyama and at paddy fields in Higashi-Hiroshima, respectively. Very high concentrations found in the soils at the industrial incinerator suggest the contamination of ashes into the soils due to uncontrolled burning in open fire and relatively higher concentrations in the paddy fields indicate the successive utilization of pesticides in the past years. Dioxins in the bottom sediments collected from Ohta River in Hiroshima City were ranged to be 1.4-6.1 pg-TEQ/dry g.PCDDs/DFs concentrations in the Seto Inland Sea bottom sediments were 0.6 to 14 pg-TEQ/dry g and their concentrations were higher in Hiroshima Bay than those at off coast, suggesting that dioxins brought by Ohta River and other rivers are accumulated in the Bay sediments. Maximum concentration of PCDDs/DFs was found in the core sediments deposited in 1970s-1980s, suggesting large production of dioxins by human activities in these decades.