The microbial contamination of stopcock entry ports attached to central venous catheters (CVC) was determined using a specially designed swab. The swab was made of a highly porous material, Porex, and was designed to fit exactly into the entry port of stopcocks. The swab was used to determine the frequency of microbial contamination of entry ports attached to CVC in patients located on an Intensive Care Unit. Of the 200 swabs obtained 44 (22%) contained microorganisms. Coagulase-negative staphylococci were recovered from 43 of the swabs and diphtheroid bacilli from 1 swab. In vitro studies were carried out to investigate the efficiency of the swab in removing excess residual fluid and organisms from entry ports. The swab absorbed relatively large numbers of bacteria within seconds. When entry ports were inoculated with between 10(3) and 10(5) cfu of either Staphylococcus epidermidis or Klebsiella pneumoniae greater than 99% of the organisms were absorbed by the swab (P < 0.01). The absorbent swab was more efficient at removing S. epidermidis from the entry port when compared to a standard cotton swab (P < 0.01). In vitro this absorbent swab reduced the potential for catheter contamination resulting from migration of organisms from the entry port via the intraluminal route. The use of the swab in the clinical situation may reduce the incidence of CVC-related infections.