Mean total symptom severity scores for subjects with experimental rhinovirus colds peak 48 h after viral inoculation. Also, total symptom scores for natural rhinovirus and nonrhinovirus colds peaked on day 2 of illness in a long-term, noncompensated epidemiology study. In contrast, the mean total symptom scores for compensated patients receiving placebo in natural cold treatment trials peaked on day 1. Comparisons by day indicated that scores for symptoms reported as occurring on day 1 in the natural cold treatment trials corresponded with experimental cold scores for symptoms reported 48 h after viral inoculation. Comparisons of frequency and cumulative distribution scores for the 2 groups indicated that natural colds in the treatment trials were of longer duration than reported. A mean total symptom severity score of <or=7 would capture 95% of experimental colds 24 h after inoculation while excluding 30.5% of natural colds on day 1 of illness. Histories given by compensated patients in natural cold treatment trials are inaccurate.