The object of the studies conducted in the years 2000–2002 on a field of 3 years’ monoculture of soybean was rhizosphere soil of soybean cultivated after tansy phacelia, winter wheat, white mustard, rye, agrimony and soybean as previous crops. The purpose of the studies was to determine the effect of cultivating the above listed previous crop plants on the formation of microorganism communities in the rhizosphere soil of soybean. The lowest total number of fungal colonies was found in the rhizosphere soil of soybean cultivated after rye and winter wheat (21.09 × 10³ and 22.58 × 10³ c. f. u., respectively), while the highest number was found in soil after soybean (36.95 × 10³ c. f. u.). The highest total number of bacteria was found in 1 g of dr yweight of the rhizosphere soil of so ybean cultivated after agrimony, and the lowest after soybean (5.80 × 10⁶ and 4.09 × 10⁶ c. f. u., respectively). The largest proportion of pathogenic fungi was characteristic of the rhizosphere soil of soybean cultivated after soybean, and the smallest – of the rhizosphere soil of soybean after agrimony as a previous crop. The dominating species among pathogenic fungi in all experimental objects was Fusarium oxysporum. The rhizosphere soil of soybean cultivated after soybean was the poorest in saprophytic fungi (35.2% of all isolations). On the other hand, the highest number of saprophytes, including antagonistic ones, was found in the rhizosphere soil of soybean after agrimony and winter wheat.