The effect of 50 Hz magnetic fields on the cytosolic calcium oscillator in Jurkat E6.1 cells was investigated for field strengths within the range from 0 to 0.40 mT root mean square. The intracellular Ca2+ concentration data were collected for single Jurkat cells that exhibited a sustained spiking for at least 1 h while repeatedly exposing them to an alternating magnetic field in 10-min intervals interposed with nonexposure intervals of the same length. The obtained data were analysed by computing spectral densities of the Ca2+ oscillating patterns for each of these 10-min intervals. For every single-cell experiment the spectra of all exposure as well as nonexposure periods were then averaged separately. A comparison between the resulting averages showed that the total spectral power of the cytosolic Ca2+ oscillator was reduced by exposure of the cells to an alternating magnetic field and that the effect increased in an explicit dose-response manner. The same relationship was observed within the 0-10 mHz (10 x 10(-3) Hz) subinterval of the Ca2+ oscillation spectrum. For subintervals at higher frequencies, the change caused by the exposure to the magnetic field was not significant.