Evidence from a strong earthquake in the Philippines provides new information to help confirm a link between radon levels in the ground and the onset of a seismic event. The authors continuously monitored the radon soil-gas concentrations near the Taal volcano, Luzon Island, from June 1993 till November 1996, finding peak levels approximately three weeks before the Mb 7.1 Mindoro earthquake (15 November 1994). Previous research had suggested that elevated concentrations of radon-222 could serve as a useful predictor of seismic events and provide an effective method of early warning, but researchers had been unable to demonstrate such a direct correlation between the two or create a method to discern the timing and location of a seismic event from radon signatures. The authors’ monitoring of this volcanically and tectonically active segment of the Pacific "Ring of Fire" revealed a near-sixfold increase in radon levels prior to the quake. After ruling out a spurious radon signal generated by the typhoon Teresa, which struck Luzon Island a few days before, the authors conclude that the Taal radon anomaly most likely originated in stress accumulation preceding the Mindoro earthquake.