1. The effect on respiration of a single dose of propranolol has been studied in normal subjects.
2. The degree of β-adrenoreceptor blockade was assessed in terms of the impaired heart-rate response to progressive exercise and the plasma propranolol concentration.
3. No effect of propranolol was demonstrated on either the ventilatory response to rebreathing CO2 in hyperoxia, or the response to progressive isocapnic hypoxia. Simple indices of maximal expiratory flow (FEV1.0% and PEFR) were also unchanged.
4. The absence of any effect of propranolol on the chemical control of breathing in man is discussed in relation to the conflicting literature.