In this multicentre, double-blind, randomized, parallel group study, 315 patients with allergic or vasomotor rhinitis were treated on a twice daily dosing schedule with either a 60 mg terfenadine-120 mg pseudoephedrine hydrochloride combination or 120 mg pseudoephedrine hydrochloride (extended release) for 2 weeks. No clinically significant differences between the two groups were noted in body weight, temperature, respiration rate or blood pressure following the treatment period. An increase in mean heart rate of approximately 5 beats/min from entry to the final clinic visit was noted in both treatment groups. No clinically significant changes were noted in either treatment group when pre- and post-treatment electrocardiograms were compared. There were also no clinically significant alterations in laboratory values, which included serum chemistry, haematology and urinalysis, within or between either group. The adverse events profiles for both groups were similar. The most frequent adverse event was insomnia, in 40 (25.3%) patients given the terfenadine-pseudoephedrine combination and in 42 (26.8%) of those given pseudoephedrine. No unusual or unexpected adverse events were reported.