This paper summarizes recent progress in CW and pulsed silicon IMPATT sources for the millimeter-wave frequency range from 30 to 300 GHz. The contrast in device structure and fabrication technology between the diodes designed for below and above 100 GHz operations is described. Current performance of IMPATT oscillators, amplifiers, and power combiners are reported. Recent activities in GaAs and InP IMPATT development are briefly discussed. Finally, system applications of millimeter-wave IMPATT sources are discussed.