Kālidāsa in the introduction to his first play Malavikagnimitram writes - Shall we neglect the works of such illustrious authors as Bhāsa, Saumilla, and Kaviputra? Can the audience feel any respect for the work of a modern poet, a Kālidāsa?
So we know he lived before Kālidāsa. As the date for Kālidāsa varies from the 1st century BCE to the 4th century CE, Bhāsa is dated between the 2nd century BCE and 2nd century CE. Based on the language used, his date is also supposed to be around 5th century BC. The plays of Bhāsa had been lost for centuries. He was known only from mention in other works like the famous text on poetics Kavyamimamsa written during 880-920 AD by Rajashekhara a famous poet, dramatist and critic. In the Kavyamimamsa, he attributes the play Svapna-vasavadatta (Swapnavāsavadatta) to Bhāsa.
Bhāsa does not follow all the dictates of the Natya Shastra. This has been taken as a proof of their antiquity as post-Kālidāsa, no play that did not adhere to the Natya Shastra's rules has been found. Bhāsa allows scenes that contain signs of physical violence to be shown on stage in plays like Uru-Bhanga.This is strictly frowned upon by Natya Shastra.
The Uru-Bhanga and Karna-bhara are the only known tragic Sanskrit plays in ancient India. Though branded the villain of the Mahabharata, Duryodhana is the actual hero in Uru-Bhanga shown repenting his past as he lies with his thighs crushed awaiting death. His relations with his family are shown with great pathos. The epic contains no reference to such repentance. The Karna-bhara ends with the premonitions of the sad end of Karna, another epic character from Mahabharata. Early plays in India, inspired by Natya Shastra, strictly considered sad endings inappropriate.
The plays are generally short compared to later playwrights and most of them draw the theme from the Indian epics, Mahabharata and Ramayana.Though he is firmly on the side of the heroes of the epic, Bhāsa treats their opponents with great sympathy. He takes a lot of liberties with the story to achieve this. In the Pratima-nataka, Kaikeyi who is responsible for the tragic events in the Ramayana is shown as enduring the calumny of all so that a far noble end is achieved.
The Duta-Vakya and Bala-charita are perhaps the only Sanskrit plays by a famous playwright with Krishna as the central character.
His other plays are not epic based. Avimaraka is a fairy tale. The unfinished Daridra-Charudatta (Charudatta in poverty) tells the story of the courtesan Vasantasena and is interesting for the same story was developed by Śhudraka into the more famous Mrichakatika on which 1984 film, Utsav by Girish Karnad is based.
His most famous play Swapna-vasavadatta (Swapnavāsavadatta)(Vasavadatta in the dream) and Pratijna-Yaugandharayana (the vow of Yaugandharayana) are based on the legends that had grown around the King Udayana, a contemporary of the Buddha. The first tells the story of how the king lost his kingdom and regained it with the help of his loyal minister Yaugandharayana and the latter of how he married the princess Vasavadatta.
Though his plays were discovered only in the 20th century, two of them Uru-Bhanga and Karna-bhara, have become popular due to their appeal to modern tastes and performed in translation and Sanskrit.
Many of Bhasa's plays are staged in Koodiyattams even now, like parts of Pratijna-Yaugandharayana,Abhisheka-nataka etc. The legendary Natyasastra scholar and Koodiyattam maestro Guru Mani Madhava Chakyar choreographed and started to perform Swapnavāsadatta and Pancharātra for the first time in the history of Koodiyattam.