Twenty-eight ragweed-allergic patients with hay fever participated in a clinical trial that examined the pattern of symptom relief resulting from addition of a cyclooxygenase-inhibiting drug to standard antihistamine therapy. In the first week antihistamine use by the subjects was standardized, and subjects were oriented to use of the hay fever symptom diary. They were then allocated, according to symptom severity, to two treatment groups. One group received 120 mg of terfenadine and 300 mg of flurbiprofen (a cyclooxygenase-inhibiting drug) per day. Members of the other group received terfenadine and a placebo that looked like flurbiprofen. This treatment lasted 1 week. Subjects recorded severity of congestion, drainage, running, nose blowing, itching, and sneezing four times each day. The flurbiprofen-treated patients experienced less severe symptoms, demonstrating maximum benefit 3 to 5 days into the drug trial with some loss of effect thereafter. Secretion-related symptoms appeared to benefit most. Combined blockade of histamine and cyclooxygenase products appears to offer improved symptom control in ragweed hay fever.