The objective of this study was to evaluate the effects of adding ketamine to standard emergency department (ED) therapy for patients with status asthmaticus. This was a prospective observational study. Ten patients with an acute exacerbation of asthma who were unresponsive to standard therapy were enrolled in the ED. Upon enrollment, children received ketamine at a loading dose of 1 mg/kg intravenously (i.v.), followed by a continuous infusion of 0.75 mg/kg/hr (12.5 microg/kg/min) for 1 hr. Clinical asthma score (CAS), vital signs, and peak expiratory flow (PEF) measurements were obtained prior to ketamine administration, within 10 min after ketamine administration was completed, and 1 hr after infusion. Median CAS on ED arrival was 15 (range 7-23) and did not significantly change immediately prior to infusion of ketamine (median 14, range 8-21). Median CAS decreased to 10.5 immediately after infusion and to 9.51 hr post ketamine infusion (37% reduction, p < 0.05 by ANOVA vs. preketamine CAS). Median respiratory rate (RR) also decreased from 39 prior to ketamine to 30 immediately following ketamine administration (25% decrease vs. preketamine; p < 0.05). Oxygen saturation significantly improved after ketamine infusion, although 5 patients remained on oxygen. Median PEF improved after infusion, but was not statistically significant. Four patients experienced mild side effects including mild hallucinations, diffuse flushing, and moderate hypertension. Side effects resolved with benzodiazepines or with discontinuation of the infusion. Addition of ketamine to standard therapy was associated with improved indices of acute asthma severity. Side effects were transitory and comparable to previous studies. However, a double-blinded randomized controlled trial needs to be conducted to determine if improvement is attributable to the addition of ketamine to standard asthma therapy.