• Eight widely used commercially available ocular decongestants were compared on the basis of vasoconstrictive effectiveness. The ability of these preparations to counteract histamine-induced erythema and to block its recurrence when rechallenged after one hour was evaluated in six human subjects in seven sessions. All vasoconstrictors tested were effective. No preparation was statistically different from 0.02% naphazoline hydrochloride in vasoconstrictive effect. In fact, this intermediate concentration of naphazoline (0.02%) was found to be significantly better than the other nonprescription decongestant preparations tested as a group and not significantly different from a group of higher concentrations of naphazoline.