The efficacy of, and tolerance to lactose-free sodium cromoglycate capsules was investigated in a multicentre trial. Data of 154 patients with asthma treated at 41 centres were evaluated over an observation period of 5 weeks. During treatment there was a significant reduction in the required dosage of concomitant medication, a marked improvement with regard to the severity of symptoms and a significant increase in peak flow rates. Assessment of treatment was "good" or "very good" in 86% of patients. Mild side effects such as cough or throat irritation were seen in only 2.6% of patients.