Coagulase-negative staphylococci (CNS) have gained substantial interest as pathogens involved in nosocomial, particularly catheter-related infections. The pathogenic potential of CNS is mainly due to their capacity to form biofilms on indwelling medical devices. In a biofilm, the bacteria are protected against antibiotics and from attacks by the immune system. The factors contributing to biofilm formation are among the best-studied virulence factors of CNS and comprise factors involved in the adhesion to a catheter surface and in cell accumulation. CNS usually persist in the host in relative silence, but may cause sepsis, for which the recently found inflammatory peptides called phenol-soluble modulins are prime candidates. Many CNS also produce several lipases, proteases, and other exoenzymes, which possibly contribute to the persistence of CNS in the host and may degrade host tissue. We are also beginning to understand how regulators of virulence trigger the expression of virulence factors in CNS. A better conception of the mechanisms underlying the pathogenicity and the frequently encountered antibiotic resistance of CNS may help to develop novel, efficient anti-staphylococcal therapeutics.