Recent progresses in the research of millimeterwave radio on fiber (RoF) systems are reported. Based on the concept of optical frequency multiplication (OFM), the theory and techniques of photonic generation of millimeterwave have been developed. These include generation of highorder optical sidemodes using eletrooptic modulators, selfheterodyne radio frequency (RF) production in photodetectors, and design of bidirectional millimeterwave RoF systems. Intermediate frequency orthogonal frequency division multiplexing (OFDM) is used to modulate the millimeterwave carrier. A comprehensive mathematic model has been set up to analyze nonlinear distortion in OFDM signals induced by optical modulator. Several experimental RoF systems operating at 40 GHz have been implemented, achieving a transmission rate of 100 Mbit/s.