The dynamics and stability characteristics of slurry loop and tank reactors were studied using continuation analysis to examine the effects of catalyst activity profiles oil reactor dynamics. The production of high-density polyethylene through the copolymerization of ethylene with hexene was studied using catalysts of the decay type (for example, TiCl4 on silica, or other Ziegler-Natta catalysts) and the buildup-type (for example, chromium oxide catalysts on silica of the Phillips type). Sustained oscillations were found to exist for decay-type catalysts in loop reactors. For both tank and loop reactors, the buildup-type catalyst exhibited isolated solution branches (isola) and multiplicity phenomena in addition to sustained oscillations. The sigmoidal shape of the buildup-type catalyst rate curve is postulated as the reason for the additional multiplicity, and isola phenomena. The implications for industrial operating conditions are discussed.