We performed 52 percutaneous lung biopsies on 34 animals (NZ rabbits) using a coaxial needle system. In 19 animals we introduced homologous clotted blood through the outer plastic cannula in order to prevent a pneumothorax. CT was used to demonstrate the pneumothorax. The aim of the experiment was to see whether clotted blood would reduce the incidence of pneumothoraces. In addition we wanted to determine the complications of this method. We found that, correctly used, clotted blood significantly reduced the incidence of pneumothoraces (31.57% as against 64.70% in the control group). It also reduced the extent of the pneumothorax. The method has no complications.