Completed symptom logs were returned by parents of 101 study children (93.5%). In addition, information from symptom logs was also collected by research assistants when acute swabs were obtained. Data on symptom severity were obtained on all 108 study children on day 1 of their cold The presence of 96 separate symptom measures in study children were compared. Twenty-one symptom measures met criteria for inclusion as candidate symptom measures (Table 4). Differences in the rates of significant runny nose and significant cough were present during the first 4 d of the illness. The most significant difference between the two groups was in the rate of significant runny nose on day 4 (50.9% in those with viral URI and 9.5% in those with no URI, p Ͻ 0.001). Although children with a viral URI were less likely to have any headache or significant headache on day 1 than those with no URI (p ϭ 0.035 and 0.048, respectively), parents of 14 children (age, 2.2-5.2 y) indicated they could not tell whether their child had this symptom. Two parents did not respond to this item on the symptom log, leading to missing headache data in 14.8% of study children. Similarly, 13 parents (12.3%) indicated they could not tell whether their child had a scratchy throat (or sore throat) on day 2. Because of the amount of missing data, neither headache nor scratchy throat was considered as candidate symptom measures.