A nuclear induction spectrometer for the measurement of short relaxation times and the study of saturation and related phenomena is described. Radio‐frequency intensities of up to 10 gauss are attainable from four to ten megacycles. Novel features of the apparatus are an rf head for use in a liquid helium cryostat, transmitter output level stabilization circuit, and a calibration circuit for comparing the intensity of the absorption at different rf levels.