Two new tubes for high-speed analogue multiplication at frequencies up to 200kc/s are described. The electrostatic field configurations required for multiplication are generated by special electrode systems which use plane electrodes, and are therefore relatively simple to construct and to mount with accuracy. The nonlinear error in prototype versions of these tubes is less than 2% of maximum output for one tube, and less than 3% for the other. The phase lag in the output with respect to either input is less than 2° for frequencies up to 200kc/s, and, with increased beam currents, the tubes are capable of operating at higher frequencies without an increase in the phase lag.It is anticipated that, with greater constructional care, an error of less than 1% of maximum output can be achieved.