To contribute more comprehensive information about the characteristics of asthma, this article analyzed patients served by the University of Alabama at Birmingham Comprehensive Asthma Program. Their physicians rated one fifth of these patients as having "severe" asthma with the remainder about equally divided between "moderate" and "mild". One in two first received a diagnosis of asthma ten or more years previously. Common comorbidities were hypertension, obesity, rhinitis, bronchitis, sinusitis, and arthritis. One half had visited an emergency room or been hospitalized for asthma in the past year. Inhaled bronchodilators and continuous theophylline were the most commonly prescribed medications. Side effects, especially tachycardia and insomnia, were common and almost exclusively associated with theophylline or corticosteroid therapy. Spirometric assessment showed chronic airflow obstruction in those with more severe asthma. Prevalence of respiratory symptoms, intensity of medication regimen, incidence of side effects, and health care utilization increased as asthma severity increased.