Background: It was hypothesized that quantitative sinus-rhythm electrogram measurements could be used to predict conduction events resulting from premature stimulation, and reentrant ventricular tachycardia inducibility. Methods and Results: Sinus rhythm activation and electrogram duration maps were constructed from bipolar electrograms acquired at 196-312 sites in the epicardial border zone of 43 canine hearts (25 with reentrant ventricular tachycardia inducible by premature stimulation and 18 lacking inducibility). From these maps, lines of electrical discontinuity where block would occur during premature excitation were estimated. The mean error in distance between the estimated and actual block line of premature excitation was 0.97cm. Based on the quantitative characteristics of the activation and electrogram duration maps and the longest block line forming during premature excitation, whether or not reentry would occur was predictable (sensitivity 94.7%, specificity 79.6%). In reentry experiments, the breakthrough point location along the unidirectional arc of block which initiated reentry was also predictable (mean error, 0.79cm). Conclusions: Sinus-rhythm measurements are useful to predict conduction events resulting from premature stimulation, and reentry inducibility.