<p>The feasibility and safety of upper calyx access in supine percutaneous nephrolithotomy (PCNL) remains controversial. We aimed to detail our technique and describe the outcomes in effectivity as well as safety in a large cohort. The authors analyzed patients with renal and proximal ureteral stones who underwent supine PCNL using upper calyx access at Rio Hortega University Hospital Valladolid (Spain) between 2013 and 2023. Patients were placed in the Galdakao-modified supine Valdivia position. Transpapillary percutaneous access to the upper calyx was guided by a combination of ultrasound (US) and fluoroscopy. Stone-free rate (SFR) was assessed by residual fragments &lt; 4&#xa0;mm assessed by non-contrast CT scan (NCCT) two months postoperatively. The 30-days complications were classified using the PCNL-specific Clavien-Dindo score. One hundred patients were included in the study. Thirty-three (33.3%) were diagnosed with staghorn stones, and 44 (44.4%) with multiple calculi. Upper calyx access was achieved supra-11th rib in 31 (31.9%), supra-12th rib in 64 (66%) and subcostal in 2 (2.1%) cases. Miniaturized PCNL was performed in 64 (64.6%) patients. Median surgical time was 117.5 (100; 150) minutes. There were no intraoperative complications and in 62.1% of the cases, a nephrostomy tube was not necessary. The median hospital stay was 3 (1; 5) days. Twenty-seven postoperative complications occurred, including 8% grade I complications. Grade II complications including the need for blood transfusion and antibiotics occurred in 5% and 9%. Grade III complications were noted in 5%, and no grade IV or V were observed. There were no significant thoracic, liver or spleen complications. The single-procedure SFR was 85%, with only 3 patients requiring a second intervention. US and fluoroscopy guided percutaneous access to the upper calyx in the supine position is feasible and demonstrates a low complication rate alongside a high SFR.</p>