Paracoccidioides brasiliensis is a fungal pathogen of humans. The P. brasiliensis response to oxidative stress is largely unexplored. We report the analysis of three catalases, PbCatA, PbCatP and PbCatC. The former are monofunctional catalases and the latter is a catalase-peroxidase. Differential expression of catalases as measured by activity and by quantitative analysis of transcripts was observed in the morphological conversion and in response to different stress conditions. PbCatA manifested higher activity in the mycelial phase, showed increased activity during transition from mycelium to yeast and during conditions of endogenous oxidative stress. Consistent with our previous studies, PbCatP manifested higher activity in yeast cells since it is putatively involved in the control of exogenous reactive oxygen species. P. brasiliensis displays an oxidative stress response following phagocytosis by macrophages, inducing the expression of catalase A and P transcripts. PbCatC displayed a relatively constant pattern of expression, being modestly induced in cells exposed to osmotic and heat stress.