The potency of a dravya which enables the same to exhibit its action is known as Veerya. Veerya is actually the ultra chemical action of the drugs which can be of two types Ushna (hot) and Shita (cold). Their translation as hot or cold is not appropriate as these denote only to the temperature status, while the veerya is something more than that. Veerya is given prime importance in classics as it decides the karma of a dravya. If the dravya becomes nirveerya, then it is considered as useless. So veerya (potency) of drug plays vital role in the treatment principles. To scrutinize the potency of the drug exothermic and endothermic reactions plays an imperative role which is exhibited here taking Atasi as an example.
Key words: Atasi, Veerya, Exothermic reaction.