Characteristic subionospheric signal perturbations referred to as 'early/fast' VLF events are found to consistently be associated with the simultaneous occurrence of unusual clusters of radio atmospherics as observed in wideband VLF data. A burst of sferic activity occurs at or before the onset of the early/fast events and lasts from several hundred milliseconds to several seconds. The cluster energy attenuates with distance more rapidly than cloud-to-ground (CG) lightning, suggesting that these clusters may be produced by intracloud (IC) lightning, and that the charge movement within the cloud may thus play a role in the causative mechanism of early/fast VLF events. ¿ 2000 American Geophysical Union