To prove the hypothesis that central venous catheter-related thrombosis and infection are associated, 43 haemato-oncological patients with an internal jugular vein catheter underwent ultrasound screening for thrombosis every 4 d. Catheter-related thrombosis was detected in 13/43 patients (30%). Catheter-related infection, as defined by the U.S. Hospital Infection Control Practices Advisory Committee, was found in 14/43 patients (33%) with colonization of the catheter in two patients, exit site infection in eight patients and catheter-related bloodstream infection in four patients. Catheter-related thrombosis and catheter-related infection coincided in 12 patients and were significantly correlated (Fisher's exact test, P < 0.0001). Detection of thrombosis indicated a catheter-related infection with a superior sensitivity (86% vs 57%) and an equivalent specificity (97%) compared with the presence of clinical signs (erythema, tenderness, warmth or swelling). Neutropenia, which occurred in 32 patients, was found in 13/14 patients (93%) with a catheter-related infection and, therefore, seemed to be an important covariate for the development of a catheter-related infection. This study showed a close correlation between catheter-related thrombosis and infection. Ultrasound screening for thrombosis was helpful for detecting catheter-related infection. These findings could be clinically useful for the handling of central venous catheters in patients with an elevated risk of infectious complications.