Abstract. An increase in the number of representatives of the legume family is important for the intensification of agricultural production, solving the problem of obtaining complete, balanced in terms of amino acid composition of food and feed. When testing varieties of mung bean (Vigna radiata (L.) Wilczek.) from the VIR collection in the ecological conditions of the Middle Volga region, varieties were identified that are able to ripen and form full-fledged seeds. When determining the germination of seed material, the germination energy varied from 70 to 100 %, germination from 96 to 100 %. It was revealed that the seeds remained unsimilar, smaller in size than the main mass. In this regard, there is a need to study the germination depending on the size of the seeds. The purpose of the research is the evaluation of the influence of seed size on sowing qualities and growth power of mung bean at the initial stages of ontogenesis. Methods. Seeds were divided into three fractions “small”, “medium” and “large”. The germination of seeds of each fraction was determined, and it was found that this process depends both on the size of the seeds and on the biological characteristics of the variety. Scientific novelty. For the first time in the conditions of the Middle Volga region, a positive correlation was found between the size of seeds and their quantitative and qualitative characteristics. Results. As a result of the research, it was found that the growth force of the studied samples was high, however, both varietal differences and differences depending on the size of the seeds were revealed. The growth force decreases in both varieties with a decrease in seed size by 3.4–10.0 %. In the Saltan sample, this tendency is more pronounced than in the Gvidon sample. But in terms of mass and volume of roots, the Gvidon sample significantly exceeds the Saltan sample. It is recommended that when cleaning and sorting mung bean seeds, the fraction that has passed through a sieve with 3 mm holes is considered waste.