Functional organ bath experiments and radiolabelled ligand binding studies were used to investigate the relationship between β-adrenoceptor-mediated relaxation and the total number of β-adrenoceptors in human lung parenchymal tissue and bronchial tissue. Sensitivity to the β-adrenoceptor agonist isoprenaline (pD 2) varied almost 10-fold (pD 2 values 6.00 to 6.85) for lung parenchymal preparations and 35-fold for bronchial preparations (pD 2 values 6.16 to 7.67) between patients. The total number of [ 3H] DHA labelled β-adrenoceptors (B max) varied almost 6-fold for lung parenchymal membrane preparations (B max 164 to 936 fmol/mg protein) and less than 2-fold for bronchial tissue membrane preparations (B max 188 to 342 fmol/mg protein) between patients. Comparison of sensitivity to isoprenaline and β-adrenoceptor number for lung parenchymal tissue from the same patient demonstrated a negative correlation (r = −0.80 [95% confidence intervals: −0.13, −0.96], 6 d.f., P < 0.05), suggesting that β-adrenoceptor-mediated sensitivity of lung parenchymal tissue is inversely related to the number of β-adrenoceptors. However, there was an absence of correlation between sensitivity to isoprenaline and β-adrenoceptor number in bronchial tissue from the same patient. Thus, the findings of the present study do not support the possibility of a direct relationship between the β-adrenoceptor-mediated responsiveness and the β-adrenoceptor number of human airway preparations.