OBJECTIVES:  The eXpeRience registry collected real world data on patients receiving omalizumab for severe uncontrolled persistent allergic asthma (SAA). Quantify the clinical benefits, health resource utilization and estimate cost-effectiveness of omalizumab compared to standard of care in the treatment of Portuguese patients with SAA. METHODS:  A cost-effectiveness model was developed to estimate the health outcomes and costs of omalizumab compared to standard-of-care. The eXperience data was used to characterize effectiveness, real world outcomes and resource utilization. Outcomes of interest were exacerbations, hospitalizations, emergency room (ER) visits, consultations and work and school absenteeism. RESULTS:  The analysis of the 62 patients demonstrated that use of omalizumab resulted in fewer exacerbations (less 6.76 exacerbations/year, fewer ER visits (less 1.86 ER visits/year), fewer consultations (less 2.81 consultations/year) and a reduction in absenteeism (less 14 days absenteeism/year). The use of omalizumab is associated to an ICER of 1,605€/avoided exacerbation. CONCLUSIONS:  : The analysis shows that the use of omalizumab is associate to better treatment outcomes and suggest that it is a cost-effective option for the treatment of SAA in Portugal