OBJECTIVES To estimate the cost and clinical implications of using subcutaneous immunotherapy (SIT) plus beclomethasone dipropionate (BDP) for the treatment of moderate and severe asthma due to house dust mites in Colombian children versus the conventional therapy with BDP. METHODS The disease course over 3 years of moderate and severe asthmatic children due to house dust mites ages 13 and 14 years and treated with BDP with or without SIT was modeled using discrete event simulation; 1000 pairs of identical patients were simulated 100 times. Population characteristics were obtained from a prevalence study in Colombia. Rates of asthma attacks were based on patient's Peak Expiratory Flow which varies according to patient's treatment. Physician visits, hospitalization and emergency room visit rates were extracted from published data. Only direct medical costs were considered; costs are reported in 2007 Colombian Pesos (COP) and inflated using the Consumer Price Index (CPI) where current costs were not available. Costs were discounted at a 3% rate. RESULTS SIT plus BDP decreased the number of asthma attacks in 70% at a cost of COP 3,315,959 per patient. Frequencies of physician visits, hospitalizations and emergency room visits were predicted to occur less frequently for patients treated with SIT plus BDP than with BDP alone. Sensitivity analyses around the time horizon, 6 and 10 years, showed increasingly better results with SIT plus BDP over time. Sensitivity analyses around the discount rate for costs were also performed. CONCLUSIONS SIT plus BDP is expected to improve outcomes and save costs compared to BDP alone. Thus, it will bring better health to Colombian children suffering from moderate-severe asthma at a savings to the Health Authorities.