Omalizumab is a monoclonal antibody that inhibits the activity of the immunoglobulin E. Omalizumab has been shown to significantly reduce asthma exacerbations and health resources utilization compared with standard therapy. A cost-utility analysis is justified to assess the economic impact of omalizumab adoption by the Colombian health care system. To estimate the cost-utility of omalizumab added to standard therapy compared with standard therapy alone in patients over 12 years old with severe allergic asthma from the perspective of the Colombian health care system. We performed a cost-utility analysis comparing direct health care costs, QALYs and exacerbations in both treatment arms. We used a Markov model to project costs and exacerbations over 20 years. Cost information was obtained from local hospital records and medication average annual consumption from a logistic operator. Exacerbations and QALYs were projected based on the scientific literature. We implemented a Monte Carlo probabilistic sensitivity analysis. Annual discount rate was 3%. Exchange rate used was 1.932 pesos per dollar (Nov 2011) Total cost [US $] of omalizumab added to standard therapy versus standard therapy alone was $90.686 IC95% (± 647,4) and $ 77.777 IC95% (± 648,4), respectively. QALYs gained was 12.07 (± 0.0032) and 11.45 (± 0.0044) for both arms. Exacerbations with omalizumab and standard therapy were 5.7 IC95% (± 0.015) and 8.7 IC95% (± 0.020), respectively. Incremental cost per QALY gained was $12.361 (± 167). Incremental cost per exacerbation avoided was $4.367 IC95% (± 55,6). According to these assumptions the incremental cost per QALY gained and incremental cost per avoided exacerbation is reasonable. But without a clear threshold in Colombia, decision is up to the evaluator.