We conducted a double-blind parallel-group study to compare the efficacy of inhaled nedocromil sodium and inhaled sodium cromogylcate in patients aged 50 years or over with asthma. Seventy-seven patients were randomized, 38 to receive nedocromil sodium (4 mg q.d.s.) and 39 to receive sodium cromoglycate (10 mg q.d.s.) over a 16-week period. Eight patients withdrew from the study. Both patient groups showed a reduction in inhaled bronchodilator usage during the treatment period. No statistically significant differences were seen in diary card PEF recordings or symptom scores. Both clinic PEF and FEV1 were significantly greater (P < 0.05) in the sodium cromoglycate group at week 12. Patients considered the treatment to be very or moderately effective in 59% of the nedocromil sodium group and 50% of the sodium cromoglycate group. Thus, the study suggests that there is no difference in response to nedocromil sodium or sodium cromoglycate in this older group of patients with asthma who are already on moderate doses of inhaled steroids.