In this book, the current advances on the functional role of molecular chaperones in protozoan's mechanisms of response to stressful conditions, as well as an overview of studies focusing on molecular chaperones as potential targets for designing novel anti-parasitic drugs, are examined. In the second chapter, the current progress regarding the structure-function relationship as well as its association with the chaperone-like activity of the mammalian PDIA1/P4HB protein are discussed. The final chapter focuses on the cytoplasmic and nuclear functions of URI/Bud27 in different organisms.