In many settings, differentiating a viral URI from other respiratory illnesses may be of trivial importance. However, for epidemiologic studies of URI or randomized controlled trials of various cold remedies, it may be critically important to more accurately differentiate patients with an actual viral infection from those with other respiratory conditions. The "gold standard" for diagnosing a viral URI, PCR (6, 7) , is expensive and requires access to sophisticated laboratory facilities, which limit its applicability for large clinical or epi-demiologic studies. Thus, other methodologies for identifying patients with viral URI may be more practical.