1, 4, 12 and 24 micrograms SOM 1397 CL, a new beta 2-adrenergic bronchodilator, were administered by inhalation to 10 healthy volunteers in a double-blind, placebo-controlled, within-subject crossover study in order to assess circulatory, tremorogenic and biochemical effects. 1 microgram SOM 1397 CL did not cause any relevant changes in the measured parameters. After administration of 4 micrograms a slight but continuous increase in tremor amplitude and c-AMP was observed. The effects on hemodynamics and other laboratory values could be considered negligible. Overdoses of 12 and 24 micrograms resulted in a dose-dependent increase in systolic blood pressure, pulse rate, tremor amplitude, alpha-AMP and lactic acid, as well as in a decrease of diastolic blood pressure and potassium. These effects may be partly attributable to beta 2-receptor stimulation. The method described in this paper can be applied as a useful tool for determination of beta 2-adrenergic activity in healthy volunteers, independent of the conventional methods which are used to evaluate efficacy of bronchodilators by the degree of bronchial muscular relaxation.