In the present study we investigate the changes in the level of serum magnesium and calcium ions, and their possible mode of regulation during progression of hibernation of the anuran, Duttaphrynus melanostictus, the Indian Common toad. Though these ions have a profound effect on the thermoregulatory center in the brain of even poikilothermic vertebrates like the Indian Common toad, not much information is available about the system. We attempt to expose the role of these ions in this system. In this animal, serum magnesium and calcium levels are known to be significantly low during the entry phase as well as during the awakening phase from the hibernation period as compared to the deepest phase. We tried to correlate the role of serum magnesium and calcium ions during different phases of this poikilothermic animal.