The purpose of this study is to determine the effects of vitamin D3 on severe asthmatic patients. Vitamin D3 may alter the response of these patients to conventional steroid therapy, making them more responsive to the latter form of treatment. Patients will be treated daily with an oral dose (2,000 IU) of vitamin D3 for one month and their clinical and serological parameters, and immune function, will be evaluated. Results from pre- and post-vitaminD3 treatment will be compared.