Urolithiasis is a growing problem. With the progress of civilization the disease affects more and more people. The most common cause of urinary tract stones are calcium oxalate deposits, which are mostly formed on the basis of metabolic disorders such as hypercalciuria and hyperoxaluria. The concentration of oxalate in the urine is an important risk factor for the formation of calcium oxalate deposits, because even slight changes in the concentration of oxalate in the urine have a greater impact on the crystallization than comparable changes in calcium concentration. Oxalate lithiasis may be caused by: oxalate metabolic disorder, excessive consumption or increased absorption of oxalate in the gastrointestinal tract. The cause of hyperoxaluria may be a genetic defect (primary hyperoxaluria) or a variety of absorption and metabolism of oxalate disorders in the intestinal tract, or the excessive consumption as a result of improper diet (secondary hyperoxaluria). Bacteria Oxalobacter formigenes – described in the 1980s – colonizes the human gut, using oxalic acid as the sole source of energy. Conditions in which there is a reduced colonization of the colon by this bacterium may promote hyperoxaluria. Studies carried out so far have shown that Oxalobacter formigenes lowers the concentration of oxalate in the intestine, the absorption is reduced, and this lowers the excretion of oxalate in the urine. In the application of this bacterium as a probiotic low oxalate diet is important. We can expect that in the future Oxalobacter formigenes will be used in the treatment of calcium-oxalate stones.