We conducted a prospective study of nasal and skin floras in 71 patients receiving chronic hemodialysis. We wished to determine whether a sterile skin preparation technique was more effective than a clean technique in removing microorganisms from the skin of the vascular access site. We also examined the effect of administration of antibiotics and status of patient hygiene on microbial flora. The presence of Staphylococcus aureus in the nose had a low predictive value for the simultaneous presence of the microorganism on the skin. The status of skin colonization can be accurately assessed only by culture of the skin. Sterile technique was no more effective at removing microorganisms from skin than was clean technique. Antibiotics significantly affected nasal flora but not skin flora. S. aureus was significantly more likely to remain on the skin after application of an antiseptic in patients with poor hygiene than in patients with good hygiene (P = 0.002). Patients with poor hygiene also had a significantly higher concentration of S. aureus on the skin of the vascular access site after application of antiseptic than patients with good hygiene (P = 0.005). We found no evidence to support a change from clean to sterile technique for skin preparation, but improvement in personal hygiene may be an effective strategy for prevention of vascular access infections.