In order to investigate the effect of beta agonist adrenergic drugs on body potassium distribution, blood samples were obtained from 30 healthy thoroughbred horses trained to horsemanship competitions, in fasting and resting conditions, before and after clenbuterol administration at eight o'clock in the morning. In each sample were determined blood glucose and plasmatic potassium concentrations.One hour after oral administration of' clenbuterol (0.8 µg/Kg), plasmatic potassium concentration was significatively lower than control values (3.9 ± 0.5 and 4.2 ± 0.2 mmol/l, respectively; p < 0.05), while blood glucose concentration (91.4 ± 20.0 mg/dl) was not significatively different from control (87.4 ± 18.9 mg/dl). At the end of' two hours after clenbuterol administration, plasma tic potassium concentration was maintained signi­ficatively lower than control values (3.8 ± 0.6 mmol/l; p < 0.05), ivhile blood glucose concentration was 90.3 ± 17.2 mg/dl. This results are indicating the participation of beta agonists, like clenbuterol, in the regulation of plasmatic potassium concentration.Con el objeto de estudiar el efecto de agonistas beta-2-adren&eacute;rgicos en la distribuci&oacute;n corporal del potasio, se tom&oacute; muestras de sangre a 30 caballos fina sangre ingl&eacute;s, cl&iacute;nicamente sanos, en pleno entrenamiento de equitaci&oacute;n, en condiciones de ayuno y reposo f&iacute;sico, en las que se determinaron niveles de glicemia y kalemia antes y despu&eacute;s de la administraci&oacute;n de clenbuterol a las 8:00 hrs. AM. Una hora despu&eacute;s de la administraci&oacute;n por v&iacute;a oral de clenbuterol (0,8&nbsp;&micro;g/kg) se observ&oacute; una disminuci&oacute;n de la kalemia (de 4,2 &plusmn; 0,2 a 3,9 &plusmn; 0,5 mmol/l; p &lt; 0,05), la que se mantuvo a las 2 horas, mientras que la variaci&oacute;n de la glicemia (de 87,4 &plusmn; 18,9 a 91,4 &plusmn; 20,0 mg/dl) no fue significativa. Estos resultados estar&iacute;an indicando la participaci&oacute;n de agonistas beta-2-adren&eacute;rgicos, como el clenbu&shy;terol, en la regulaci&oacute;n del potasio plasm&aacute;tico. &nbsp; &nbsp; &nbsp;