Omalizumab has demonstrated therapeutic benefits in controlled clinical trials. Evaluation of outcomes in real-world clinical practice is needed to provide a complete understanding of the benefits of omalizumab treatment. eXpeRience was a 2-year, international, single-arm, open-label, observational registry that evaluated real-world effectiveness, safety and use of omalizumab therapy in 943 patients with uncontrolled persistent allergic asthma. Effectiveness variables (physician's Global Evaluation of Treatment Effectiveness [GETE], and change from baseline in exacerbation rate, symptoms, rescue medication use, and oral corticosteroid [OCS] use) were evaluated at pre-specified time-points. Safety data were also recorded. By physician's GETE, 69.9% of patients were responders to omalizumab after 16 (±1) weeks. The proportion of patients with no clinically significant exacerbations increased from 6.8% during the 12-month pre-treatment period to 54.1% and 67.3% at Months 12 and 24, respectively. Symptoms and rescue medication use at Month 24 were reduced by >50% from baseline. Maintenance OCS use was lower at Month 24 (14.2%) compared with Month 12 (16.1%) and baseline (28.6%). Overall, omalizumab had an acceptable safety profile. The results from eXpeRience indicate that omalizumab was associated with improvements in outcomes in patients with uncontrolled persistent allergic asthma; these improvements were consistent with the results of clinical trials.