Abstract: A portable microprobe uses 10 gigahertz CW microwave radiation at a power level of less than 10 milliwatts for recording of a number of biophysical phenomena associated with the cardiac and neural activity of the life system. The microprobe consists of a Gunn diode feeding power into a short, insulated dielectric waveguide, the free end of which houses a point contact semiconductor diode isolated by a metal shield from the incident beam. The wave guide concentrates and delivers a pencil shaped beam into the tissue of interest and the back-scattered radiation is modulated and detected by the diode. The detected signal is filtered, amplified and recorded to reflect on-going biological activity. The receiver electronics is housed in a small self-contained package and has its output connected through a flexible attachment to two ear tubes which enable continuous monitoring of the audio response through an electrical and audio converter indicative of the on-going biological activity.