Reactive distillation (RD) is a great process intensification concept applicable to equilibrium limited reaction systems, but how can anyone decide quickly if RD is indeed worth applying? To answer this question, this study proposes a mapping method for checking the applicability of reactive distillation (RD). The initial development is for one of the most relevant subset of quaternary reversible reactions (A + B reversible arrow + D, with boiling points T-b,T-c < T-b,T-A < T-b,T-B < T-b,T-D), by using only basic chemical (equilibrium and kinetics) and physical (relative volatilities) parameters. Generic cases, assuming ideal thermodynamics and constant parameters, are used to obtain a set of RD applicability graphs that provide broad insights into the RD operation. In addition, the new mapping method provides reasonable estimates of the RD applicability to real (non-ideal) chemical systems based on the available pre-defined maps (which are actually applicability graphs of the generic ideal cases). This new approach leads to a straightforward estimation of the applicability of RD to real systems, prior to performing any rigorous process simulations and without any clear-cut decision making (as used in previous studies).