Omalizumab, a monoclonal anti-immunoglobulin E (IgE) antibody, is being successfully used as supplementary therapy to improve asthma control in children with severe persistent allergic asthma from the age of ≥6 years. Because the majority of commercially available IgE assays measure free as well as omalizumab-bound IgE, a rise in total IgE is believed to occur in the course of therapy. We aimed at testing the therapeutic monitoring regime based on total IgE measurements in patients treated with omalizumab over a period of 12-60 months. We report on 10 patients aged 8-17 years who were given omalizumab to treat severe allergic bronchial asthma. Total IgE in serum (sandwich immunoassay ADVIA Centaur; Siemens Healthcare Diagnostics GmbH, Eschborn, Germany) was determined before injection of omalizumab. In two patients, the dose of omalizumab was reduced during the treatment once the patients' total IgE was in the normal range. Six months after the start of treatment with omalizumab, all patients showed a marked drop in total IgE levels compared with baseline (p < 0.003). All patients tolerated omalizumab well. The dose reduction in two patients with normal total IgE levels caused no clinical deterioration. The rise in total IgE levels after treatment with omalizumab, which has been reported in the literature, was not confirmed in the present study. Extensive elimination of IgE by omalizumab influences the immune system and IgE regulation. This will be an important aspect of dosage in long-term therapy. Patients undergoing treatment with omalizumab must be monitored at close intervals.