BACKGROUND Percutaneous nephrolithotomy (PNL) is the standard procedure for patients with renal stones over 2 cm in diameter. We analyzed complications after this procedure focusing on two different methods of tract dilation. MATERIAL AND METHODS Between August 2008 and April 2016 222 percutaneous nephrolithotomies were performed in a total of 208 patients. The Group I (n=123) comprised patients where Alken dilatators were used, while Group II (n=99) comprised patients where Amplatz dilators were used. Efficacy was examined based on ultrasound and x-ray examination one month after the procedure. Complications were recorded using Clavien Dindo classification. RESULTS Efficacy was 85.3% and 86.8% in group I and II, respectively (p=0.77). Grade I complications were present in 14.6% and 3%, grade II were present in 9.7% and 8%, grade IIIa were present in 2.4% and 2%, grade IIIb were present in 1.6% and 2%, grade IVa were present in 1.6% and 7%, grade IVb were present in 3.2% and 1% in Group I and Group II, respectively. These differences were statistically significant (p=0.03). CONCLUSIONS Efficacy was comparable between Alken dilator and Amplatz dilator groups. In group I, there were more postoperative fevers >38.5 °C and a higher rate of urosepsis. On the other hand, in group II we observed more pleural injuries. All differences resulted from the type of access to the kidney (inter/infracostal), punctured calyx, and utilization (or not) of access sheath rather than type of dilators itself.