Abstract: A capacitive probe assembly is comprised of an electrode subassembly and an electric circuit subassembly which can be readily connected to and disconnected from each other, both mechanically and electrically. The electrode subassembly comprises a measuring electrode and a guard electrode concentrically mounted within a tubular, electrically conductive housing while being insulated from each other and from the housing. The measuring and guard electrodes are exposed through one of the opposite open ends of the housing. Inserted in the housing through the other open end thereof, the circuit subassembly includes a circuit board, with measuring circuit elements mounted thereon, which is supported at one end by a plug and at another end by a disclike support. The plug is engaged in sockets in the measuring and guard electrodes for both mechanical and electrical connection of the measuring circuit board to the electrodes.