This paper proposes a simplified mathematical and tabular method for assessing the risk of exothermic runaway reactions, based on the calculated hazard index. Intrinsic elements, such as reactivity stability, exothermic enthalpy, etc., are presented as measures of severity of a potential runaway event. Similar v, extrinsic elements, such as risk and safety factors associated with operating conditions, are considered as measures of the likelihood of an event. All intrinsic and extrinsic parameters, with proper weightings, are converted into a runaway risk index (RRI). The chemical process risk. can therefore be quantified and divided into six levels based on the normalized RRI extremely high, high, moderate, mild, low, and very low. They can be further classified into tolerable and intolerable risks. Sample runs on methanol-acetic anhydride esterification, cumenebydroperoxide decomposition, and decompositions of ammonium nitrate, are presented to illustrate the validity of the method.