Once the research assistant determined that a study child had met criteria for a clinical cold, the parent was asked to begin completing the daily symptom diary. The scoring system used in the diary was based on the Jackson score and other cold severity rating systems and included measures for 12 separate symptoms for each day of the cold, for up to 14 d (8,10,11). Symptoms included sneezing, runny nose, nasal congestion, cough, fever, headache, malaise, chilliness, scratchy throat, sore throat, hoarseness, and myalgias. Each morning, for as long as symptoms persisted, parents were asked to rate the severity of each of these symptoms using the scale: 0 ϭ none, 1 ϭ mild, 2 ϭ moderate, and 3 ϭ severe. An additional possible response was "can't tell," which was added because it was felt that it would be difficult for parents of young children to rate the presence and severity of some of these symptoms. In an attempt to standardize the reporting, a guide for rating severity of symptoms including examples of symptoms warranting a particular severity was provided to all parents of study children. The guide for rating symptoms is shown in Table 1 .