OBJECTIVES Poor asthma control is associated with increased healthcare cost in patients with moderate or severe asthma. Here we evaluate the impact of omalizumab on poor asthma control events (PACE) and medication utilisation (MU) in a case-crossover study of US patients with moderate or severe persistent asthma. METHODS Truven MarketScan database was used to compare PACE (hospitalisation, ER visit, corticosteroid [CS] burst or ≥7 short-acting beta-agonist [SABA] fills) and MU for 1 year pre/post omalizumab exposure, during the period 1-January-2007 to 30-September-2012. Included in the analysis were patients aged ≥12 years who had 1 inpatient or 2 outpatient Asthma claims (ICD-9=493.XX) and used omalizumab continuously for 1 year, with 2 years continuous coverage (1 year pre/post omalizumab index date). Patients were categorized as Moderate or Severe based on their most recent 8 weeks of continuous, NHLBI-guideline-recommended, therapy preceding omalizumab. RESULTS In total, 429 patients (mean age, 46.6 years; female, 59.0%; Moderate=340, Severe=89) were included in the analysis. Omalizumab was associated with reductions in proportions of All, Moderate, and Severe asthma patients with PACE (41.3%, 48.3%, 17.2%, respectively; all p<0.05). Specifically, reductions in patients with ≥1 asthma-related hospitalisation , ≥1 asthma-related ER visit,  ≥2 CS bursts, and ≥7 SABA fills in the Moderate group (Moderate: 55.9%, 77.8%, 53.8%, and 40.6%, respectively; all p≤0.0196) drove reductions in All patients (all p≤0.0159). Reductions in patients with ≥1 OCS fill and ≥1 SABA fill were observed in All and Moderate patients (20.3%–26.1%; all p<0.0001); reductions in mean OCS fills and mean SABA fills were observed in All and Moderate patients (26.0%-42.5% p<0.0001), while reductions in mean SABA fills were also observed in Severe patients (20.1%; p=0.0328). CONCLUSIONS Omalizumab initiation was associated with significant reduction in PACE and MU in patients with moderate or severe persistent asthma.