Renal ultrasonic scanning was performed before and after 57 consecutive kidney biopsies in order to assess the value of this method in the diagnosis of complications. One large and six small perirenal haematomas were found, corresponding to an incidence of 13%. This figure is considerably larger than the incidence found with conventional diagnostic methods, but smaller than with computed tomography. One hydronephrosis and a blood clot in the urinary bladder were also diagnosed. No clinically significant complications were missed. We recommend ultrasonography as the first diagnostic procedure when biopsy complications are suspected.