Several different mechanisms have been suggested for the natural stimulation of Pc 1 geomagnetic pulsation events. These mechanisms include hydromagnetic noise in the magnetopshere, bursts of radiation from high-energy charged particles, or sferics from lightning discharges. Guided by the results of experiments to generate Pc 1 pulsations by VLF transmissions into the magnetosphere, and by the theory that has been developed in support of these experiments, we now propose a new mechanism: the stimulation of Pc 1 pulsation events by naturally occurring repetitive VLF signals. The VLF signal may be echoing whistlers, periodic chorus elements, or other periodic or quasi-periodic VLF wavetrains echoing along a geomagnetic field line. Preliminary support for this hypothesis is provided by a comparison of the Pc 1 pulsations and VLF activity occurring at Roberval, Quebec, during 9 intervals of simultaneous Pc 1 pulsation and VLF measurement.