Complications of CVCs in 382 consecutive patients receiving a stem cell transplantation (SCT) were analysed. Early complications were pneumothorax (3.6%), haematothorax (0.5%), dislocation (3%) and dysfunction (3.6%). Eighty-seven-associated infections (22%) were observed, leading to removal of the CVC in 26 patients. More bacteraemias were associated with double- or triple-lumen CVCs, 19% vs 5% in single lumen CVCs (P < 0.0001). Coagulase-negative staphylococci were the predominant microorganisms in 72%. A special point of investigation was CVC-associated thrombosis and the prophylactic value of nadroparin. Two consecutive regimens with nadroparin were used and compared; 7 days 2850 IE nadroparin and 10 days 5700 IE nadroparin. The incidence of CVC-associated thrombosis was 6.9% in 382 patients with 390 catheters. The incidence was 8% in patients receiving one of the prophylactic nadroparin regimens compared to 6% in a comparable control group without prophylaxis. A short course of nadroparin was unable to prevent thrombotic complications after discontinuation.