Desirable features of new generation intensive care ventilators include the ability to ventilate a wide range of patient sizes, an uncomplicated control panel, an appropriate but not excessive variety of ventilatory patterns, adequate patient monitoring and alarm functions, and simplicity of cleaning and routine maintenance. Examples of currently available ventilators include the Servo 900-C, CPU-1, Engstrom Erica, Bear 5, Drager EV-A and Hamilton Veolar. The incorporation of microcomputer control into some of these ventilators has resulted in improved flexibility and a limited number of automatic responses to detected patient changes. However, the function of components provided to allow spontaneous ventilation, such as demand valves, requires considerable improvement. Current trends in ventilator design include further refinement of computer control and the provision of graphic displays showing the results of continuous sophisticated analysis of respiratory function. The extent to which these developments will prove clinically useful will require careful evaluation.