© 2015 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved. Introduction Robot-assisted laparoscopic pyeloplasty (RALP) has been gaining acceptance among pediatric urologists. Over 300 have been described in the literature, but few studies have evaluated the role of RALP in infants alone. Objective We sought to examine the operative experience and outcomes of RALP in a cohort of infants treated at multiple institutions across the United States. Our primary aim was to describe the safety and efficacy of RALP within this cohort. We recognize the challenges of performing minimally invasive surgery in small patients. In our paper, we address some technical considerations for the infant population. Study design This multi-centered observational study collected data on subjects one year of age or less who underwent RALP between April 2006 and July 2012 at five institutions. The primary outcome was resolution of hydronephrosis, and secondary outcomes included surgical time and complications. Results A total of 60 patients (62 procedures) underwent RALP by six surgeons during the study period. All surgeons had >5 years of experience beyond fellowship training. Mean surgical age was 7.3 months (SD ± 1.7mo), 56 patients (95%) were diagnosed prenatally, and 59 patients (95%) had follow up imaging. Of these patients, 91% showed resolution or improvement of hydronephrosis. Two patients had recurrent obstruction and required additional surgery. Mean surgical time was 3 hours 52 minutes (SD ± 43 minutes). Seven (11%) patients reported intra-operative or immediate post-operative complications.Gender (male)44 (73)Prenatal Diagnosis56 (93)Laterality Left32 (53) Right26 (43) Bilateral2 (3)Surgical Age (months)7.29 (±1.7)Surgical Weight (kg)8.1 (7.1-9.2)Surgical Time (hr:mm)3:52 (±0:43)Length of Stay1 (1-2)Intra-operative Complication1 (2)Immediate Post-op Complication6 (10)Resolution (n = 59) Resolved1 (1.7) Improved53 (89.8) Stable4 (6.8) Worsening1 (1.7) Data in table given as n (%), mean (±SD), or median (25th - 75th percentile). Discussion This series found a 91% success rate for reduction or resolution of hydronephrosis, and an 11% complication rate. This is equivalent to modern series comparing open pyeloplasty to pure laparoscopic and robotic-assisted laparoscopic pyeloplasty, which report success rates ranging from 70-96%, and complication rates ranging from 0-24% for open pyeloplasty. We lacked a standardized technique amongst institutions. This was not surprising since there are not established technical benchmarks for this surgery. However, we specified multiple technical considerations for this unique patient population. Conclusion The advantages of using robot-assistance to perform pyeloplasty in infants remain to be defined. This study cannot make that assessment due to small sample size. Nonetheless, this cohort is the largest robotic pyeloplasty series in infants to date. Seeing an excellent success rate and a low complication rate in this infant cohort is encouraging.