Most rhinovirus serotypes use intercellular adhesion molecule-1 (ICAM-1) as the receptor to enter cells, but ICAM-1 expression has not been detected on normal nasal epithelial cells. During experimental rhinovirus infection, expression of ICAM-1 on nasal epithelial cells was examined with immunohistochemical staining of nasal scrape biopsy specimens, and levels of soluble ICAM-1 in nasal lavage fluid were measured by sandwich enzyme-linked immunosorbent assay technique. Expression of ICAM-1 on nasal epithelial cells increased following inoculation in 20 of 23 infected subjects. The median number of ICAM-1-positive cells per 6.25-mm(2) area of stained biopsy specimen was 0 in control samples (day 20 or 33 after inoculation), and in those without infection, 6 on day 1 (P< or =.05), 14.5 on day 3 (P< or =.01), 1.5 on day 5, and 0 on day 9. In a different group of volunteers, soluble ICAM-1 in nasal lavage fluid was higher on days 1 and 3 compared with preinoculation levels (P< or =.001), but only 11 of 23 infected subjects had a 2-fold or greater increase. Up-regulation of ICAM-1 receptor expression on nasal epithelial cells occurred within 24 hours after inoculation in experimental rhinovirus infections (prior to onset of symptoms) and declined promptly by day 5.