Our experimental and theoretical investigations in the field of new semiconductor sources of coherent mid/far-IR radiation based on the intracavity nonlinear mixing of close-in-frequency optical fields in dualwavelength diode lasers are reviewed. Perspective schemes of quantum-well heterolasers of this kind are considered, and the ways of increasing the power of difference-frequency radiation are suggested, including the use of mode-locked lasers and hybrid surface-emitting grating-outcoupled lasers.We discuss newly-designed schemes of intracavity nonlinear-mixing diode lasers, which may be used for the difference-frequency generation of coherent mid/far-infrared and terahertz radiation. They are based on a standard heterolaser technology, which guarantees high compactness, reliability, continuous-wave room-temperature operation, and low threshold injection pumping.We review recent experimental results on the sum-, double-and difference-frequency generation of coherent radiation in various types of semiconductor lasers paying particular attention to schemes designed and fabricated by our group, first of all, a Laser with Asymmetric Waveguide Design [1], a Tunnel-Junction Laser [3], and a Butt-Joint Laser [4]. Fig.136 ,(((