We have investigated the use of subcutaneous terbutaline in 17 patients with brittle asthma and five patients with chronic severe asthma. Twelve of the 17 patients with brittle asthma improved both subjectively and objectively (mean lowest daily PEF rising from 142 litres/min to 297 litres/min), with reduction in oral steroid dose, nebulized beta-agonist dose and number of hospital admissions. Both continuous infusion and 6-hourly divided dose regimens were equally effective. Only one of the five with chronic severe asthma showed any lasting response. Eighteen patients have continued to use subcutaneous terbutaline over long periods (2-40 months). Overall 11 patients suffered side-effects of usually minor degree, although one patient had to withdraw because of the development of painful subcutaneous nodules. We conclude that subcutaneous terbutaline delivered by infusion or by intermittent injections is a useful addition to the therapy of some patients with brittle asthma.