The batch reactor is a dynamic system whose trajectory depends on various parameters. Parametric sensitivity signifies large changes in the reactor trajectory induced by small changes in parameters across threshold values. This is a form of critical behavior and can lead to runaway conditions, resulting in unsafe reactor operation. In this paper experimental results of three exothermic chemical systems are considered : (a) the homogeneous liquid phase reaction between sodium thiosulfate and hydrogen peroxide, (b) the heterogeneous (liquid-liquid) hydrolysis of acetic anhydride catalyzed by dilute sulfuric acid, and (c) the noncatalytic heterogeneous (liquid-solid-gas) hydrogenation of nitrobenzene using Sn and HCl. The systems are modeled using pseudohomogeneous rate expressions available in the literature. The only measured variables are the initial compositions and the reactor temperature as a function of time. Effect of several parameters, i.e., initial temperature, catalyst concentration, initial composition, etc., on the reactor trajectory are discussed. Existing criteria in the literature are used to determine the parametric sensitivity of these systems.