Establishing a clinical diagnosis of catheter-related infection, especially catheter-related bloodstream infections is often difficult. The diagnosis typically is based on clinical and laboratory criteria, with each having significant diagnostic limitations. Among the different techniques the quantitative culture of the distal segment of the catheter by the method described by Brun-Buisson is recommended. More recently, two techniques were proposed in order to establish or to eliminate a catheter-related sepsis without removing the catheter. The first technique is based on the comparison of the result of quantitative culture of paired blood samples, one obtained through the central catheter ant the other from a peripheral venipuncture site. The second technique is based on the measurement of the differential positivity times (DPT) of blood cultures drawn simultaneously from central venous catheter and peripheral vein. At the present time, the published studies do not allowed a reliable comparison between the results obtained with these different techniques. The choice of the technique is fully dependent on the informations you want to collect: surveillance of colonization or catheter-related infection diagnosis, as well as on the type of catheter, the duration of catheterization and the preciosity of the catheter.