Five hundred and fourteen soil samples collected from 78 sites in Japan were analyzed for their contents of trace and ultra-trace elements. We estimated the background levels (natural abundance) of 57 elements in soils. The concentration ranges were so wide that the ratios of the highest values to the lowest values were more than 100 for all the elements, with the exception of Be, Ga, Mo, Ag, In, Sn, and Ba. While the concentrations of the first transition elements (2ISC to soZn in atomic numbers) were higher than the concentration of the other elements, those of lighter (sLi and 4Be) and heavier elements tended to decrease, with an increase or decrease of atomic numbers, with the apparent exception of Pb, Th, and U. Concentrations of elements with even atomic numbers were, in most of the cases, higher than the concentrations of both adjacent elements with odd atomic numbers. Frequency distribution of most of the elements was strongly positively skewed. Markedly positive correlation coefficients (r>0.9) were observed among the elements within the same group in the Periodic Table in many combinations. The dendrogram obtained by cluster analysis showed that the occurrence and distribution of the elements in soils were mostly controlled by the chemical properties of each element, rather than by the nature and properties of individual soil samples. The total contents of the elements in soils were strongly dependent on the chemical composition of the parent rocks from which respective soils were derived.Key Words: background level, trace and ultra-trace elements.Basic information on the background levels, or the natural abundance, of elements in soils is required for studies on the behavior of elements in the soil-plant systems. In recent years, there has been an increasing concern about the concentrations of various trace and ultra-trace elements in environmental samples. In spite of this growing interest and although a total of only 90 elements were involved CH to 92U in atomic numbers, with the exception of the man-made 4S Tc and 6IPr), most of the soil scientists appear to have paid most attention to a limited number of beneficial elements (B, Mn, Fe, Cu, Zn, and Mo) and selected
