Seventeen subjects with chronic severe asthma completed a 48 week prospective, double blind study with crossover of treatment at 24 weeks, in which triamcinolone acetonide 80 mg intramuscularly every four weeks was compared with oral prednisolone 10 mg daily. Spirometry, twice daily measurements of peak expiratory flow rate, and self assessment of asthma symptom scores showed significant improvement during triamcinolone treatment; less extra prednisolone was required and there was significant weight loss. Two patients withdrew, one because of dissatisfaction with prednisolone and one because of side effects while taking triamcinolone. Three were withdrawn, one with proximal muscle weakness and two because of intercurrent illness. Adrenal suppression, bruising, and hirsuitism were worse with triamcinolone, other side effects being comparable. On completion of the study 16 of the 17 patients opted to continue taking triamcinolone acetonide. This treatment is an important addition to the therapeutic options available for chronic severe asthma.