Objective: To determine whether the use of mist improves clinical symptoms in children presenting to the emergency department (ED) with moderate croup. Methods: Children 3 months to 6 years of age were eligible for the study if they presented to the ED with moderate croup. Moderate croup was defined as a croup score of 2-7. The patients were randomly assigned to receive either mist (humidified oxygen) via mist stick or no mist. The patients had croup scores measured at baseline and every 30 minutes for up to two hours. At these intervals the following parameters were also measured: heart rate, respiratory rate, oxygen saturation, and patient comfort score. The patients were treated until the croup score was less than 2 or until two hours had elapsed. All patients initially received a dose of oral dexamethasone (0.6 mg/kg). Other treatments, such as racemic epinephrine or inhaled budesonide, were given at the discretion of the treating physician. The research assistants were unaware of the assigned treatments. Results: There were 71 patients enrolled in the study; 35 received mist and 36 received no mist. The two treatment groups had similar characteristics at baseline. The median baseline croup score was 4 in both groups. The outcomes were measured as the change from baseline at 30, 60, 90, and 120 minutes. The change in the croup score from baseline in the mist group was not statistically different from the croup score change in the group that did not receive mist (p = 0.39). There was also no significant difference in improvement of oxygen saturation, heart rate, or respiratory rate at any of the assessment times. There was no adverse effect from the mist therapy. Conclusions: Mist therapy is not effective in improving clinical symptoms in children presenting to the ED with moderate croup.