1 The purpose of the study was to assess and compare the effects of inhaled salbutamol on heart rate (HR), finger tremor (Tr) and specific airways conductance (sGaw) in the measurement of 32-adrenoceptor blockade in normal subjects. 2 Five healthy volunteers were given oral doses of atenolol 50 mg, 100 mg, 200 mg (AS0, A100, A200), propranolol 40 mg (P40) or identical placebo (P1) in a single-blind crossover design. 3 Three hours after drug ingestion, dose-response curves were constructed using cumulative doses of inhaled salbutamol: 200 ,g, 700,ug, 1700 ,ug, 3200 ,ug, 6200,ug. HR, Tr and sGaw were measured at each dose increment, made every 20 min. 4 Increasing doses of atenolol were associated with progressive reduction in salbutamol induced ,-adrenoceptor responses. The greatest attenuation occurred with propranolol. These effects on ,B-adrenoceptor responses were similar for HR, Tr and sGaw. Geometric mean dose ratios (compared with placebo) for AS0, A100, A200 and P40 were as follows HR: 1.98, 2.75, 4.29; Tr: 1.60, 3.78, 6.34, 80.50; sGaw: 1.08, 4.35, 12.30, 66.0 (no dose ratio was obtained for HR with P40). 5 These results showed that atenolol and propranolol attenuated the effects of salbutamol on HR to a similar degree as Tr and sGaw. Furthermore, the variability was least in the measurement of chronotropic responses, suggesting that this may be used to quantify 132-adrenoceptor antagonism. The B1-adrenoceptor selectivity of atenolol was a dosedependent phenomenon, although the 132-adrenoceptor blockade of A200 was much less than with P40.