Plant growth promoting rhizobacteria (PGPR) represent a wide variety of bacteria inhabiting the root surface and root vicinity. They are directly or indirectly involved in promoting plant growth and development via production and secretion of various regulatory compounds in the rhizosphere. PGPR are generally beneficial to a wide range of crops including maize. The main objective of this study was to determine the effect of PGPR strains on the microbial abundance in maize rhizosphere. The trial was conducted at Rimski Šančevi experimental field of Institute of Field and Vegetable Crops in Novi Sad, Serbia. The trial included five maize hybrids (NS 3014, NS 4015, NS 5043, NS 6010 and NS 6030) developed at the Institute and three treatments with microorganisms. Non-inoculated treatment was control. Inoculation was performed with Bacillus Q7, Pseudomonas PS2 and their mixture with Azotobacter chroococcum (Q7 + PS2 + AC). Application method was incorporation immediately before planting with liquid culture of strains (density 109 CFU/ml). It was observed that the certain treatment with rhizobacteria increased the number of all three studied microbial groups in the rhizosphere of the same hybrid. The best effect on the number of microorganisms in the rhizosphere of NS 6010 was achieved with Q7 + PS2 + AC, in NS 5043 with Q7 and with PS2 in NS 4015. The results obtained in this study indicate the importance of PGPR in crop production, which requires a constant expansion of knowledge about the mutual interactions of plants and microorganisms.