The maximal binding volume (Bmax) of beta-adrenoreceptor in the lung tissues of guinea-pigs in health group, experimental asthma group and ear acupuncture treatment group was determined with radiological ligand binding analysis. The results were as follows: (1) the Bmax of beta-adrenoreceptor in lung tissues of guinea-pigs in asthma group (52.4 +/- 20.1 fmol/mg protein) was significantly lower than that of healthy group (106.8 +/- 14.0 fmol/mg protein) (P < 0.01); (2) the Bmax in the lung tissues of guinea-pigs in ear acupuncture treatment group (84.5 +/- 35.1 fmol/mg protein) was significantly higher than that of asthma group (P < 0.02), and was similar to that of healthy group(P > 0.05). These suggested it was one of the mechanisms of ear acupuncture treatment on asthma to increase the number of beta-adrenorecepor in the lung tissues.