The safe observation time following pediatric renal transplant biopsy is unknown. To predict the safety of day-care pediatric renal transplant biopsy, we retrospectively evaluated the timing, incidence and severity of post-biopsy complications in children observed overnight. Biopsies were performed under real time ultrasound guidance using an 18-gauge Bard Biopty needle. Coagulation screen and platelet counts were measured preprocedure. Hemoglobin (Hb) was measured preprocedure, at 6 h and at 1-day post-procedure. Twenty-eight of 45 children transplanted between January 2002 and May 2004 underwent 65 biopsies. There was gross hematuria following 8 (12%) biopsies; 2/8 occurred after 6 h. Hb fell by >15 g/L in six cases (9%) - three had Hb drop within 6 h post-procedure and three had a steady decline over 24 h. No patient required blood transfusion. Oral analgesia post-procedure was required in seven cases (11%). One of these had gross hematuria. No patient required surgical intervention or transfusion. Three complications were recorded >6 h post-biopsy but none required intervention. Daycare renal transplant biopsy appears to be safe in selected patients.