This paper presents a 125GHz LC-VCO dedicated to mmW applications. It has been designed, within the framework of the European project DOTFIVE, with a new B3T bipolar technology developed by STMicroelectronics, in which NPN transistors reach a ft and fmax of 260GHz and 340GHz respectively. Under a nominal power supply of 1.8V, the 125GHz VCO dissipates 54mA (with output buffers) for a measured phase noise of –75dBc/Hz at 1MHz offset from the 125GHz carrier and achieves a tuning range of 2GHz with a size of 0.25 mm2.