Study Type – Therapy (case series) Level of Evidence 4 What's known on the subject? and What does the study add? Laparoscopic pyeloplasty has replaced open pyeloplasty as the new standard of care and we, among others, have even proven its applicability to redo surgery. The focus is now on limiting morbidity. One technical modification to this end is transmesocolic (TM) exposure of the PUJ. This randomized study pinpoints the objective benefits of TM exposure of the PUJ compared with standard colon reflection, and its results showed a 23% conservation in operating time. OBJECTIVE To compare the efficacy and safety of colon‐reflecting (CR) and transmesocolic (TM) laparoscopic pyeloplasty approaches in a prospective randomized non‐selective setting. PATIENTS AND METHODS Excluding only those patients with a history of abdominal surgery, all consenting patients scheduled for laparoscopic pyeloplasty of left‐sided pelvi‐ureteric junction (PUJ) obstruction between December 2004 and November 2007 were randomized into one of two groups: laparoscopic pyeloplasty using the standard CR approach or laparoscopic pyeloplasty through the TM aperture. All patients underwent dismembered repair by a single expert and were followed by diuretic renogram and urography at 4 months postoperatively and by annual diuretic renogram thereafter. Four discrete task phases were timed for comparison: trochar to PUJ, dismembering and spatulation, stenting and anastomosis. RESULTS Sixty‐four patients were randomized into two groups, TM or CR, with 32 patients in each. The groups were similar, with no significant difference in sex, age, initial renal function or body mass index. Forty‐seven patients were ≤15 years old. The mean (sd) operating time was 23% shorter in the TM group, owing mostly to the much shorter trochar to PUJ phase (5.0 [3.2] min in the TM group vs 35.8 [10.3] in the CR group; P < 0.001). The mean hospitalization time was shorter in the TM group than in the CR group (2.9 vs 3.6 days; P < 0.001). Thirty‐one of 32 patients in each group (96.9%) achieved a durable cure. CONCLUSION Transmesocolic exposure of left‐sided PUJ obstruction is superior to standard CR exposure, in that it saves anaesthesia time, hospitalization time and has lower morbidity with no compromise in efficiency, and could be considered as the new standard approach.