Our objective was to evaluate the safety and diagnostic efficacy of the ultrasound-guided renal biopsy procedure using an automated biopsy device (Biopty gun) with a 14-gauge needle. Five hundred fifteen consecutive ultrasound-guided renal biopsies performed in two large university hospitals were retrospectively reviewed. Three hundred forty-five biopsies were performed on renal allografts and 170 on native kidneys. The tissue specimen was adequate for histological evaluation in 95.3% of the cases (94.8% in the transplanted kidney group, 96.5% in the native kidney group). The overall complication rate was 12.2% and was significantly higher in the native kidney group (19.4%) than in the renal allograft group (8.7%). Major complications occurred in 2.7% of the cases (2.9% of the renal allografts and 2.4% of the native kidney biopsies), including one procedure-related death and the loss of the renal allograft in two other patients. Minor complications were noted in 9.5% of the biopsies and there were significantly more in the group of the native kidneys (17.1%) than in the group of the transplanted kidneys (5.8%). Renal biopsy with an automated device using a 14-gauge needle has a high tissue recovery rate, but it is associated with a small risk of serious complications.