Central venous catheters (CVC) have proven to be a reliable route of the administration of chemotherapy, saline, blood cells and nutritional support in patients with malignant haematological disease. However, infection remained one of the most important causes of morbidity associated with this procedure. The aims of this study were a) to evaluate the efficacy of laminar air flow to prevent CVC infections, b) to study morbidity associated with polyethylene (PE) and silicone (S) catheters, and c) to evaluate the part played by increasing staff practice. 177 CVC were inserted in 170 children during a period of 20 months. Ages ranged from 5 months to 15 years (mean: 7 years). All the S CVC were tunnelled whereas, because of their rigidity, none of the PE CVC were. At the time of their removal, bacteriological samples from the CVC skin exit site, blood drawn through the catheter and the tips of these CVC were cultured. During the first period (one year), three groups of CVC were studied: in group 1, 37 S CVC in patients placed in a non-sterile ward; in group 2, 40 S CVC in children nursed under laminar air flow; in group 3, 60 PE CVC in patients of a non-sterile ward. During the second period (8 months), 40 new S CVC were inserted in children nursed in non-sterile wards, but after nursing staff training (group 4).(ABSTRACT TRUNCATED AT 250 WORDS)