The use of central venous catheters (CVC) carries a risk from local and systemic infectious complications, with prevalence of 6% in patients in Intensive care unit. Microorganisms colonizing the CVC usually originate from patient's or staff member's skin, but the source can also be a contaminated infusion solution or hematogenous dissemination from a distant focus. The infective agents often show increased resistance to antibiotics, which is an additional therapeutic problem. There is no knowledge of the frequency of the colonization of CVC by microorganisms in hospitals in Bosnia and Herzegovina, neither of the types of microorganisms which usually colonize CVC, nor their sensitivity to antimicrobial agents. During the period 2004-2008, the analysis of 188 CVC samples was performed in patients in ICU at which the doubt for CVC connected infection was present. The microorganism identification was performed by standard microbiological antibiotics sensitivity methods. Out of 188 checked samples, 101 (54%) had positive cultures and 87 (46%) were sterile. Out of 101 positive microbiological cultures, in 33 (32.67%) the gram-positive bacteria had been found, gram-negative in 62 (61.37%) and Candida albicans in 6 (5.94%) cultures. Gram-ne-gative bacteria were 93.55% sensitive to imipenem, and Gram-positive bacteria were sensitive to vancomycin. Gram-negative bacilli and Coagulase-negative staphylococci are the most frequent micro-organisms which colonize the CVC. The increase of bacteria antibiotics resistance represents a big problem. All those facts leads to the need for bigger control and supervision over the CVC implantation, its proper maintenance and rational use.