The aim of the studies was to record the influence of selected plants on the population and activity of some physiological groups of soil microorganisms. Studies were performed on a model of plot experiment (Department of Detailed Plant Cultivation, University of Agriculture in Lublin) set in 1999 on brown soil developed from loess-like dusts at the Experimental Station in Felin. The following plants were cultivated: kaszubska vetch (Polish origin), Siberian vetch, chickling vetch, Sida hermaphrodita, Helianthus tuberosus, konopianka osier and American osier. Soil samples for analyses were taken from the rhizosphere zone. Microbial and biochemical analyses were carried out three times at plant’s different developmental stages. It was found that in general the studied plants favored the development of cellulolytic bacteria, reduced the growth of amylolytic and lypolytic ones and diminished the total number of bacteria. They stimulated the development of hypha fungi, with the exception of Helianthus tuberosus and American osier that inhibited their growth. Therefore, the most favorable ratio of bacteria to fungi was recorded under these plants. It was the worst under papilionaceous plants and Sida hermaphrodita . Probably the development of hypha fungi, which had optimum conditions for growing due to the acidic reaction, was the reason. Fairy great oscillations of released carbon dioxide amounts were observed. Therefore, Helianthus tuberosus and American osier showed the most favorable influence on useful communities of soil microorganisms.