As a precursor to a planned randomized controlled trial of the efficacy of Echinacea purpurea in preventing viral URIs in pediatric patients, we collected respiratory samples using nasal swabs on children with a clinical cold for PCR testing against respiratory viruses. Parents of these children completed comprehensive symptom diaries during the episode. Our goal was to identify a set of symptoms that could be used to develop a prediction rule that differentiated children with a viral URI from those with negative viral testing.