The design and construction of an Overhauser Effect Spectrometer operating at X band is described. The ESR section is a Varian V‐4502 spectrometer equipped with a 9‐in. electromagnet and a shim coil assembly. NMR detection is based on a broadband rf hybrid juction feeding a coil in an X‐band quartz dielectric cavity. Signal processing is carried out at a constant intermediate frequency of 25.1 MHz with a Varian V‐4311 fixed frequency rf unit. The mixing scheme employed to translate the NMR information to 25.1 MHz is described. Medium resolution performance (resolution ∼10−6) for the NMR is achieved under field‐frequency locked conditions. The lock is based on a Super‐Regenerative Oscillator (SRO) housing a control sample, and operating as a field‐tracking frequency source. This SRO injects into an oscillator which excites the analytical sample resonance and also serves as a local oscillator, thereby making the locked spectrometer multinuclear in capability. Typical Overhauser effect recordings of protons and fluorines are presented.