The dynamics and stability of three gas-phase reactions in fixed-bed reactors are analysed employing multi-step rate models and single-step Langmuir-Hinshelwood rate equations. It is found that multi-step models increase the regions of asymptotic stability and are in general less conservative in predicting the hot spots. As our earlier work showed that these rate models correlate the data accurately as compared with single-step equations, it is suggested that the reactor behaviour predicted by the multi-step models be taken as the reference to judge the performance of any other simplified model. © 1982.