Sixty-six Chinese patients with rhinitis, with or without asthma, were randomly allocated to a course of injections either with E. pteronyssi-us extract or placebo. The course consisted of 18--22 weekly injections, followed by monthly maintenance injections with the highest concentration for 1 year. Progress was evaluated by a patient's daily diary and monthly assessments by the physician, by comparisons of skin and nasal challenge tests and by the specific serum IgE concentration, before treatment, at the end of the weekly course, and once during the maintenance course. No improvement was detected at the end of the weekly course, but during maintenance there was a consistent benefit to the patients receiving the D. pteronyssinus extract both in the diary and the physician's assessment, especially the former. There was no consistent change in the skin or nasal challenge tests and there was a trivial fall in the serum IgE levels in the patients on the extract. Adverse reactions were much more common in the patients on the extract, but most were trivial. The different methods of assessment used and the role of hyposensitization with D. pteronyssinus are discussed.