Previous investigations of the peroxidase-oxidase reaction indicate the existence of a period-doubling route to chaos at pH 5.2 and a period-adding route at pH 6.3. In the present study, we extend these results in two regards : (i) The reaction was studied at a series of intermediate pH values under otherwise identical conditions. The new experiments suggest that the transition from period-doubling to period-adding takes place at approximately pH 5.4 and is characterized by a loss of dynamical complexity. (ii) A detailed model (Bronnikova, T. V.; Fed’kina, V. R.; Schaffer, W. M.; Olsen, L. F. J. Phys. Chem. 1995, 99, 9309-9312) was shown capable of reproducing the principal experimental results. These include the shift from period-doubling to period-adding, the existence of narrow regions of period-doubling between adjacent mixed-mode oscillations in the period-adding regime and changes in cycle amplitude.