Catheters can become colonized with microorganisms through exoluminal (catheter insertion site) or endoluminal (hub and infusates) routes. It has been shown that, the longer a catheter remains in place, the more important the endoluminal route becomes. The endoluminal route of infection can be prevented to some extent when an antibiotic solution is instilled in the catheter for a long enough time and on a regular basis. However, to avoid resistance from occurring, the use of antibiotics in such a lock for infection prevention should remain exceptional. Although there is evidence to support the concept, methodologically appropriate clinical data on the use of antiseptic solutions for this purpose are still awaited.