An Extension Study of Xolair in Moderate to Severe, Persistent Asthma Patients Who Completed Study Q2143g

Inclusion Criteria: * Successful completion of the 24-week study period in Study Q2143g * Signed informed consent (in the case of a minor, consent must be given by the child's parent or legally authorized representative) * For subjects who have never received Xolair, a serum IgE level \>=30 IU/mL and \<=1300 IU/mL and have a body weight \>=20 kg and \<=150 kg * Females of childbearing potential must, in the opinion of the investigator, be using an effective method of contraception to prevent pregnancy and agree to continue to practice an acceptable method of contraception for the duration of their participation in the study. Exclusion Criteria: * Thrombocytopenia as evidenced by a platelet count of \<100,000/uL * Pregnant or breastfeeding * Significant systemic disease (e.g., infection, hematologic, renal, hepatic, coronary heart disease or other cardiovascular diseases, endocrine or gastrointestinal disease) within the previous 3 months * History of neoplasia * Any systemic condition requiring regular administration of an immunoglobulin * Known hypersensitivity to any ingredients of Xolair, including excipients (sucrose, histidine, polysorbate 20) * History of noncompliance with medical regimens * Current participation in a study using an investigational new drug other than Xolair * Participation in Study Q2195g