ABSTRACT: The choice of production technologies for heavy oil reservoirs hinges on robust determination of both hydrocarbon volume and viscosity. Lateral and vertical disposition of hydrocarbon as well as variations in oil properties must be quantified along with their associated uncertainties for optimizing production strategies. This paper introduces a new approach to the characterization of heavy oil reservoirs, integrating nuclear magnetic resonance (NMR) with dielectric dispersion measurements and conventional nuclear porosity logs in a single self-consistent workflow that provides reliable fluid saturation and oil viscosity. The complementary information content and commensurate sensitive volumes of dielectric and NMR logging tools make these measurements natural choices for heavy oil evaluation. Whereas conventional resistivity-based analysis may be challenged by the fresh or variable salinity formation water in many heavy oil reservoirs, dielectric logs provide robust saturations even in fresh water environments. The method builds on recent advances in NMR viscosity estimation techniques that enable accurate viscosity determination for crude oils with viscosities ranging from tens to millions of centipoise. NMR diffusion measurements as well as relaxation time distributions can be incorporated in the analysis. The method is valid for any NMR acquisition sequence, tool design, or conveyance method and ensures that radial as well as axial responses of the respective measurements are properly considered. Monte Carlo sampling is used to derive uncertainties on fluid volumes and viscosities, which can be fed in decision-making processes that rely on these quantities. Although particular attention is paid to the integration of wireline NMR, and dielectric measurements, the method is quite general and may be adapted to conventional resistivity measurements in place of dielectric logs and LWD in place of wireline logs. Examples are presented that demonstrate the application of the method in a range of very different heavy oil reservoirs.