Background:Catheter Related Blood stream Infections (CRBSI) are prevalent and a potentially fatal complication pertaining to cardiovascular implant devices. There have been no major studies on bacterial colonization of catheters in cardiovascular patients in Iran.Objectives:To evaluate the incidence of catheter colonization of bacteria in the largest Iranian cardiovascular center.Patients and Methods:March 2011 to 2012, Cauterization procedures performed on 60 patients hospitalized in Rajaie Cardiovascular Medical and Research Center, Tehran, Iran, with arterial or venous catheterization, inserted 48 hours or more, catheter evaluations done by culture methods. Blood cultures were also obtained simultaneously.Results:Forty-four out of 60 catheters (73.3%) were positive with a significant colony count. Of 44 positive cases, 11 patients had positive blood culture. Three most frequently isolated microorganisms were Staph Albus [14 (32%)], Entrococcu [12 (27%)] and Acinetobacter [5 (11%)]. gram-positive cocci were sensitive to Vancomycin and Linezolid and gram-negative bacilli were sensitive to Amikacin, Gentamicin, Tobramycin and Imipenem.Conclusions:The study findings revealed that the catheter infection in our patients had sources other than normal skin flora. These results will assist in determining the possible source of the infections, furthermore, how they are transmitted, moreover aid in controlling and preventing these dangerous in- infections.