Application of fluidic elements in ventilator technology has resulted in the development of mechanical ventilators for the use in the therapy of acute respiratory failure. We have tested a new apparatus of this type, the Monaghan 228, in the technical laboratory and in clinical use. The results of this study can be summarized as follows: the technical performance of the Monaghan 228 is comparable to that of sophisticated electrically powered and controlled ventilators. The delivered tidal volume remains quite constant with variations of the opposing resistance and with the application of positive end-expiratory pressure. The differences between set and delivered oxygen concentrations do not exceed 4.5% at different tidal volumes. The ventilator has been used in a surgical intensive care unit during the last two years. More than 100 patients have been treated for a total of over 500 days. Clinical experience leads us to conclude that the Monaghan 228 is a versatile, reliable ventilator which can be used for a wide spectrum of diseases requiring mechanical ventilation.