Inner surfaces of PVC central vessel catheters used in the treatment of mature and premature newborns for periods between 6 h and 12 days were examined by scanning electron microscopy. Fibrin in form of plain facets, polypous, lamellar of fibrillar-reticular agglomerations were seen at the surfaces of all examined catheters. Red blood cells and platelets attached to the fibrin or interspersed into the fibrin network were discovered. One catheter was completely occluded and a dense mycelium of candida albicans was found within the network. Fibrin depositions at the surfaces of central vessel catheters can probably be the cause of numerous complications e.g. embolic events and catheter-induced infections.