Disclosed are novel mesogenic compounds, liquid crystal compositions (liquid-crystalline media) comprising them and suitable for high-frequency technology, and high-frequency devices using them, such as phase shifters, antennas, tunable filters, switching devices, e.g. operated in the microwave region, to a process for preparing the compositions. The liquid crystal compositions have high optical anisotropy, a positive dielectric anisotropy and a wide temperature range of nematic phases.