['The safe duration of warm ischemia during partial nephrectomy remains controversial.', 'Our aim was to evaluate the short- and long-term renal effects of warm ischemia in patients with a solitary kidney.', 'Using the Cleveland Clinic and Mayo Clinic databases, we identified 362 patients with a solitary kidney who underwent open (n=319) or laparoscopic (n=43) partial nephrectomy using warm ischemia with hilar clamping.', 'Associations of warm ischemia time with renal function were evaluated using logistic or Cox regression models first as a continuous variable and then in 5-min increments.'] Does every minute count when the renal hilum is clamped during partial nephrectomy?