Esmolol is an ultra short-acting beta 1 adrenergic- receptor antagonist reported to have no intrinsic sympathomimetic activity. It has been successfully used in lowering the ventricular rate and rate-pressure product in patients with myocardial infarction, post myocardial infarction angina, or acute unstable angina (Kirshenbaum et al., 1985). In anaesthetized dogs, esmolol produced steady-state beta-blockade within 20 minutes of initiation of 3 hours i.v. infusions and did not produce alpha-blockade (Gorczynski and Vuons 1984). The aim of the present work is to investigate the effect of esmolol on some cardiovascular and respiratory functions. In addition. Its effect on duodenal and uterine smooth muscles was also studied.