Despite continuous advances in the treatment of long bone fractures, disturbances of healing processes remain a difficult challenge. Currently, autologous cancellous bone and bone marrow grafting has become the standard treatment of delayed unions and non-unions. Platelet concentrates rich in growth factors – platelet-rich plasma (PRP) – represent a novel osteoinductive therapy that could be valuable for the treatment of disturbances of bone healing processes. This article reports the efficiency of percutaneous autologous platelet-leukocyte rich gel (PLRG) injection as a minimally invasive method as alternative to open grafting techniques. Following the outpatient procedure, each of 32 participants was followed up on a regular basis with clinical examinations, roentgenograms, dual-energy x-ray absorptiometry (DEXA) examinations and functional evaluations. In the delayed-union group the average time to union after PLRG injection was 9,3 weeks and the union was achieved in all cases. In the nonunion group, the union was observed in 13 of 20 cases and the average time to union after PLRG injection was 10,3 weeks. Interestingly, in patients with non-union, who a union was not achieved, the ave time from the fracture and/or from the last operation was longer than 11 months. Probably the fibrous tissue in the gap interposing the bone ends becomes more ossified with time and the vascular vessels diminish, so the PLRG is no longer able to induce the bone healing processes in such cases. This is our initial experience with the use of PLRG as biologic treatment for delayed union or nonunion. Our investigation showed that percutaneous PLRG injection in delayed union is a sufficient method to obtain union, which is less invasive procedure than bone marrow injection. Also percutaneous PLRG grafting can be an effective method for the treatment of selected cases of nonunion. One critical factor is the average time of PLRG injection to the index operation – the time less than 11 months after initial surgery seems to be critical to achieve good outcomes in percutaneous PLRG injections for nonunion.