Background: The introduction of automated biopsy devices and the localization of the kidney by ultrasound were aimed at optimizing efficacy and safety of the percutaneous renal biopsy procedure. We evaluated these technological advances in our renal biopsies performed in children. Methods: We sequentially used the Silverman needle (1969–1974), the TruCut needle (1974–1990), and the automated Biopty device (1990–1996). Fluoroscopy was used to localize the kidney until 1985, ultrasound examination prior to biopsy from 1985 to 1992, and direct ultrasound guidance since 1992. A total of 962 native kidney biopsies and 119 allograft biopsies were performed. Results: In the native kidney biopsies, the introduction of the Biopty device and ultrasound guidance were independently associated with fewer passes required to obtain adequate tissue and more glomeruli per specimen. The rate of biopsies yielding more than 9 glomeruli increased from 69 to 92% (p < 0.05). The number of glomeruli harvested per centimeter core length was inversely related to patient age (p < 0.01). More appropriate cortical tissue was retrieved in renal allograft biopsy specimens with the application of the new techniques. The occurrence of macroscopic hematuria (9.6%) in the native kidney biopsies was not affected by the puncture or localization technique applied, but subcapsular hematomas were documented more often with the Biopty device (42%) than with the TruCut needle (16%), probably due to improved ultrasound equipment. In the whole series 2 patients died, and 3 others required renal surgery and 4 blood transfusions. Conclusions: The automated ultrasound-guided procedure is a feasible and reliable technique for percutaneous renal biopsy in children. It gives a greater yield of diagnostic tissue without increasing the rate of clinical complications.