Intravenous catheters, artificially infected with staphylococci by perfusion experiments were investigated by Scanning Electron Microscopy (SEM), to demonstrate the mode of adhesion. It seemed to be clear, that the first step of bacterial attachment was associated with the different irregularities of the inner surface of the catheter. With longer perfusion times and/or heavier inoculum cell adherence took place also in apparently smooth regions of the catheter lumen. The possible utilization of catheter material was discussed.