The breeding work on soybean at the Agricultural Institute Osijek primarily has aimed to increasing yields of soybean in Croatia. The improving of yield potential is based on the improvement of genetic basis of traits that determine its quantity and quality, applying the conventional breeding methods and outlines valid for self-pollinated crops, such as soybean. The objective of this research was to evaluate grain quality of new developed soybean elite breeding lines in comparative tests with standards into 00, 0 and I. maturity group (MG) during a three-year period (2001-2003) in Osijek. Tested elite breeding lines have developed from different hybridization within the Institute's soybean breeding program and have chosen on the basis of their performances. Standards are released cultivars of the Institute that have grown in commercial production in Croatia. The grain quality value of tested genotypes was estimated through analysis of level and stability of protein and oil content in grain, respectively. After stability analysis, on the part of tested materials which showed high level and good stability in both protein and oil content in grain, were made analysis of triacylglycerols. The obtained results of biometrical analysis in this study showed that the most tested promising lines had significantly higher protein and oil content in grain in relation on standards into MGs 00, 0 and I, as well as good stability in analyzed traits. Analysis of triacylglycerols showed genetic variability in this trait. Generally, these data indicate on achieved genetic improvement of domestic soybean lines in grain quality.