3D numerical simulations of unipolar electrograms (EGs) and hybrid monophasic action potentials (HMAPs) were performed by using the cardiac Bidomain model with homogeneous and heterogeneous Luo–Rudy I membrane models. While estimating local recovery times from EGs can be difficult in case of flat T-waves or linear ST ramps, the HMAP signal always displays a monophasic downstroke as does the transmembrane action potential (TAP) and contains valuable information for assessing repolarization time. The simulation results show that: (a) the HMAP fast repolarization time is a reliable estimate of the TAP fast repolarization time; (b) the HMAP ending (90%) repolarization time is a less reliable estimate of the TAP ending repolarization time; (c) analogous conclusions hold for the associated action potential durations APD and APD90.