Using Silicon as the substrate material, silicon monolithic millimetre-wave integrated circuit (SIMMWIC) oscillators and receivers are successfully realised. For the coplanar oscillators, a slot is used as the resonant structure in which a monolithically integrated IMPATT diode, selectively grown by silicon molecular beam epitaxy (Si-MBE), acts as the negative resistance device. Pulsed and CW operation of the planar oscillators is achieved in the 90 GHz region. The output power is radiated directly from the resonant slot. Complete receivers, with monolithic Schottky diodes together with the antenna, are integrated on a single chip. The suitability of the chips for near-range measurements is pointed out.