Charak Samhita (1500 B.C.)
This treatise is written by Aacharya Agnivesha and revised by Aacharya Charak. It deals with the Ayurvedic aspects of internal medicine. It is considered to be the most ancient medical treatise in India. It deals with different aspects of disease and treatment. It is divided in eight parts or Sthanas, each of which bears a lot of information about all the aspects of Ayurveda. It is an extensive work, comprising of around 12,000 verses. It contains most important principles of internal medicine along with the description of many diseases. However, there are no surgical methods mentioned in the text.

Sushrut Samhita (1000 B.C.)
This treatise, written by Aacharya Sushrut, deals with surgery, ophthalmology and ENT. It is the first treatise, which consists of the detailed and systematic description of surgery along with operative procedures of many diseases. It also contains the description of principles of medicine and brief description of the rejuvenating therapy as well as aphrodisiac therapy.

Ashtang Samgraha and Ashtang Hruday (100 A.D.)
These are the compilations of Charak Samhita and Sushrut Samhita. Vagbhata, reffered to as Vruddha -Vagbhata. The work of this book is a compilation (Samgraha) of information, explanations and prescriptions from Charak Samhita and Sushrut Samhita. Though the work is not original, still, the value of the work is undoubtedly great, for it has neatly collected the essential details from the two classics, which are too extent, rambling and descriptive.