One hundred and fourteen umbilical catheters (79 arterial and 35 venous) were cultured with a semiquantitative technique. Twelve cultures were SQC positive with ≥15 colonies, and all but two of these had ≥100 colonies. Organisms usually considered to be pathogens were associated with SQC positive catheters, whereas organisms generally considered nonpathogens were associated with <15 colonies on SQC. Therefore SQC may help to differentiate between contamination and infection related to umbilical catheters. The one case with purulence at the cord base grew 100 colonies of Staphylococcus epidermidis on SQC. S. epidermidis showed a bimodal distribution in colony count and should be considered as a pathogen when high colony counts are present. Duration of catheterization was longer in SQC positive catheters. Empiric antibiotic use was associated with negative SQC. Further study is indicated in a newborn population with a lower rate of antibiotic use for correlation of SQC results with catheter-induced bacteremia and sepsis.