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BACKGROUND High quality of evidence comparing mini percutaneous nephrolithotomy (mPNL) with standard percutaneous nephrolithotomy (sPNL) for the treatment of larger-sized renal stones is lacking. OBJECTIVE To compare the efficacy and safety of mPNL and sPNL for the treatment of 20-40mm renal stones. DESIGN, SETTING, AND PARTICIPANTS A parallel, open-label, and noninferior randomized controlled trial was performed at 20 Chinese centers (2016-2019). The inclusion criteria were patients 18-70 yr old, with normal renal function, and 20-40mm renal stones. INTERVENTION Percutaneous nephrolithotomy PNL was performed using either 18 F or 24 F percutaneous nephrostomy tracts. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS The primary outcome was the one-session stone-free rate (SFR). The secondary outcomes included operating time, visual analog pain scale (VAS) score, blood loss, complications as per the Clavien-Dindo grading system, and length of hospitalization. RESULTS AND LIMITATIONS The 1980 intention-to-treat patients were randomized. The mPNL group achieved a noninferior one-session SFR to the sPNL group by the one-side noninferiority test (0.5% [difference], p <  0.001). The transfusion and embolization rates were comparable; however, the sPNL group had a higher hemoglobin drop (5.2 g/l, p <  0.001). The sPNL yielded shorter operating time (-2.2 min, p = 0.008) but a higher VAS score (0.8, p <  0.001). Patients in the sPNL group also had longer hospitalization (0.6 d, p <  0.001). There was no statistically significant difference in fever or urosepsis occurrences. The study's main limitation was that only 18F or 24F tract sizes were used. CONCLUSIONS Mini mPNL achieves noninferior SFR outcomes to sPNL, but with reduced bleeding, less postoperative pain, and shorter hospitalization. PATIENT SUMMARY We evaluated the surgical outcomes of percutaneous nephrolithotomy using two different sizes of nephrostomy tracts in a large population. We found that the smaller tract might be a sensible alternative for patients with 20-40mm renal stones.