Using the biomagnetometer superconducting quantum interference device (SQUID), the magnetic signals relating to spontaneous uterine activity were measured for the first time in 25 women with uterine leiomyomas, and 12 women with normal, non-leiomyomatous, uteri. Magnetic radiation, in the range of low frequency (below 2 Hz), was of low amplitudes in normal uterine tissues and of high amplitudes in benign leiomyomas. The observed differences were confirmed by the corresponding power spectra obtained from the statistical Fourier analysis. It is suggested that biomagnetic measurements may facilitate the detection of uterine leiomyomas in equivocal cases.