Forty-two ragweed hay fever patients participated in a study which examined the profile of symptom relief provided by terfenadine, and the relative adequacy of symptom control with the drug given from the beginning of the season compared with treatment started after symptoms were well established. Compared with placebo, terfenadine effectively relieved sneeze, itch and eye symptoms. It had no effect on running, blowing and drainage. Subjectively perceived congestion benefited marginally. When the drug was begun after symptoms were well established, sneezing responded quickly and maximally. Eye discomfort lessened but not to the level experienced by those dosed from the beginning of the season. The pattern in other symptom categories was less clear. Overall, terfenadine improved all rhinitis symptoms except those related to hypersecretion. Some symptoms appeared to respond better when drug dosing commenced at the beginning of the season.