1. Regulation of the flow and pressure of the respiration gas in a respirator during the respiration cycle in which the actual flow and pressure of the respiration gas are measured via a measuring device arranged proximate the patient connection and the measured values thereof are converted into electrical signals and in which the flow and pressure of the respiration gas are controlled during the inspiration and expiration portions of the respiration cycle via valve means arranged between the respiration gas source and the measuring device, comprising: measuring the actual flow of respiration gas proximate the patient; measuring the actual pressure of respiration gas proximate the patient, calculating nominal values of flow and pressure from preselected fixed values and said actual values; comparing the actual values measured for the flow and pressure with said nominal values; and obtaining from said comparison a control signal for modulating the valve means and thereby regulating the flow and pressure of the respiration gas wherein the inspiration portion of the respiration cycle is comprised of two phases, and wherein said regulation includes pressure-regulating the first of said two phases and flow-regulating the second of said two phases.