Continuous subcutaneous insulin infusion (CSII) is a commonly used, safe intensive insulin therapy method effective in maintaining normoglycaemia. The disadvantage of CSII are skin infections of the catheter injection site. The aim of the study was to gain insight on the colonization of subcutaneous insulin pump catheters by skin flora and to investigate the correlation between Staphylococcus aureus carrier state (presence in the nose), its presence on the skin and catheter. 141 catheters obtained from 94 children with T1DM and CSII were examined using the semi quantitative culture technique of Maki. The result was positive in 34 examinations (24.1%) in 30 children (31.9%). Most often coagulase negative staphylococci were isolated (30), mainly Staphylococcus epidermidis, 1/3 of the staphylococci were methicillin resistant. S. aureus was detected in 7 examinations in 6 children. S. aureus carrier state was proved in 31.9% of all examined patients, more often in children with a positive catheter culture (41.4%), there were no MRSA. No correlation between S. aureus carrier state and catheter colonization was shown. Statistically significant correlations between: coagulase negative staphylococci presence, including the methicillin resistant strains, on the skin and on the catheter surface (p< 0.0001); glycosylated hemoglobin (HbA1c) and bacteria catheter colonization (p = 0.0335) were observed. Subcutaneous catheter colonization by microorganisms often occurs in CSII. Microorganisms found on the skin are the most frequent cause of the subcutaneous catheter infection.