Details are given of the construction and performance of a "crossed coil" induction head, for the detection of nuclear magnetic resonance in 0.1 cm³ specimens, in which the condition of maximum sensitivity is achieved through the operation of a single manual control. The simple method of construction provides, at the optimum setting, a decoupling of 80 dB between the coils which remains constant to within 0.4 dB over a period of a week.