Abstract: Mitochondria from diverse species can undergo a massive permeability increase known as the permeability transition, a process first thought to be an artifact. It is currently accepted that in the inner mitochondrial membrane there is a mitochondrial unselective channel (MUC), also known as the permeability transition pore. Regardless of the species, MUC opening leads to uncoupling of oxidative phosphorylation. In each species, MUC regulation appears to be different, probably as a result of the adaptation of each organism to its specific environment. To date, the components and the putative physiological role of MUCs are still a matter of debate. Current hypothesis suggest that proteins normally participating in diverse metabolic functions constitute MUCs. Among these proteins, the adenine nucleotide translocase and the phosphate carrier have been proposed as putative MUC components in mammalian and yeast mitochondria. In this review, the characteristics of MUCs from different species and strains are discussed. The data from the literature reinforce the current notion that these channels are preserved through evolution albeit with different control factors. We emphasize the knowledge available of mitochondrial unselective channels from different yeast species.CI - Copyright (c) 2010. Published by Elsevier B.V.