Limited data support the use of first-generation antihistamines for treatment of the common cold. The purpose of this study was to test the effectiveness of clemastine fumarate, a first-generation antihistamine, for treatment of sneezing and rhinorrhea associated with naturally occurring common colds. Four hundred three subjects (202 clemastine fumarate recipients and 201 placebo recipients) who reported new onset (< 24 hours) of cold symptoms that included rhinorrhea or sneezing were studied. At baseline (day 1), the mean symptom-severity scores +/- SEM for the clemastine fumarate and placebo groups were not significantly different. The mean rhinorrhea-severity score +/- SEM was not different on day 2; however, on day 3, the mean rhinorrhea-severity score +/- SEM was 1.02 +/- 0.07 for the clemastine fumarate group and 1.39 +/- 0.07 for the placebo group (P < .001). This treatment effect persisted on day 4. A significant effect on sneezing was noted on days 2-4. Sedation occurred in 14% of the clemastine fumarate-treated subjects and 1.5% of the placebo-treated subjects (P < .0001).