A method of mapping cardiac repolarization activity, comprising: receiving an electrogram signal S(t) comprising a unipolar electrogram signal from an electrophysiology catheter at a signal processor; and using the signal processor: identifying a local activation time ("LAT") tick time within a preset window about a reference time T ref; defining the LAT tick time as a depolarization tick time T D for the preset window; computing a first derivative S'(t) of the electrogram signal S(t) for the preset window; identifying (508, 510) a repolarization tick time T R using local maxima and local minima of S'(t); and computing an activation recovery interval for the preset window using the depolarization tick time T D and the repolarization tick time T R, the method being characterized by that identifying a repolarization tick time T R using local maxima and local minima of S'(t) comprises: identifying a maximum tick time T max and a minimum tick time T min within a preset refractory window ΔRW surrounding the depolarization tick time T D using S(t); computing a LAT amplitude L 1 using S(T max) and S(T min); identifying a next cycle tick T next occurring after T max using S(t); determining a search period following the depolarization tick time T D for the repolarization tick time T R; identifying a time T SLM during the search period at which S'(t) reaches a local maximum; identifying a time T slm during the search period at which S'(t) reaches a local minimum; and defining the repolarization tick time T R using one or more of T SLM and T slm. receiving an electrogram signal S(t) comprising a unipolar electrogram signal from an electrophysiology catheter at a signal processor; and using the signal processor: identifying a local activation time ("LAT") tick time within a preset window about a reference time T ref; defining the LAT tick time as a depolarization tick time T D for the preset window; computing a first derivative S'(t) of the electrogram signal S(t) for the preset window; identifying (508, 510) a repolarization tick time T R using local maxima and local minima of S'(t); and identifying a local activation time ("LAT") tick time within a preset window about a reference time T ref; defining the LAT tick time as a depolarization tick time T D for the preset window; computing a first derivative S'(t) of the electrogram signal S(t) for the preset window; identifying (508, 510) a repolarization tick time T R using local maxima and local minima of S'(t); and computing an activation recovery interval for the preset window using the depolarization tick time T D and the repolarization tick time T R, the method being characterized by that identifying a repolarization tick time T R using local maxima and local minima of S'(t) comprises: identifying a maximum tick time T max and a minimum tick time T min within a preset refractory window ΔRW surrounding the depolarization tick time T D using S(t); computing a LAT amplitude L 1 using S(T max) and S(T min); identifying a next cycle tick T next occurring after T max using S(t); determining a search period following the depolarization tick time T D for the repolarization tick time T R; identifying a time T SLM during the search period at which S'(t) reaches a local maximum; identifying a time T slm during the search period at which S'(t) reaches a local minimum; and defining the repolarization tick time T R using one or more of T SLM and T slm. identifying a maximum tick time T max and a minimum tick time T min within a preset refractory window ΔRW surrounding the depolarization tick time T D using S(t); computing a LAT amplitude L 1 using S(T max) and S(T min); identifying a next cycle tick T next occurring after T max using S(t); determining a search period following the depolarization tick time T D for the repolarization tick time T R; identifying a time T SLM during the search period at which S'(t) reaches a local maximum; identifying a time T slm during the search period at which S'(t) reaches a local minimum; and defining the repolarization tick time T R using one or more of T SLM and T slm.