This review focuses on the present knowledge about beneficial free-living soil bacteria that associate closely with plant as plant growth-promoting rhizobacteria (PGPR). Growth promotion can occur mainly by two mechanisms (1) directly by phytohormone production (e.g. gibberelin, auxin and cytokinin) or enzymatic lowering of plant ethylene levels (ACC deaminase), nitrogen fixation, iron chelating by siderophores, phosphorum solubilization or (2) indirectly by the reduction or prevention of the action of plant pathogens. The properties of PGPR offer a great promise for agronomic applications. This review presents examples of its application in practice.