The effect of years and locations on the soybean seed protein and/o oil contents was analyzed using the chemical component data of 4 culrtivars or breeding lines from 5 locations of the Regional Uniform Soybean Test from 1987—1989. The results showed that a significant change in the protein or oil contents occured between years or locations. The percent protein, oil, and protein plus oil were varied at the ranges of x±1.586%, x±0.706%, and x±1.156% respectively, due to the year—location effect.