Kausitaki Samhita is one of the old recensions of Rig Veda. Kaushitaki Samhita is different from Sankhayana Samhita, the other school of Rig Veda still prevalent in different parts of the country. There are certain differences between the two recensions.
Kausitaki Samhita is known to have been prevalent in the oral tradition of the Nambudiri Brahmins of Kerala about sixty years ago, though no manuscript is known to exist. It was long assumed by historians of Vedic literature and others that Kausitaki and Sankhayana were the names of one and the same school of Rig Veda.
Pandit Bhagvad Datta was the first to examine this problem, and he concluded that Kaushitaki was different from Sankhayana. He further stated that there were four divisions of the Sankhayana – Sankhayana, Kausitaki, Mahakausitaki and Sambavya, and pointed out that the first one was represented by the different texts of this school – Samhita, Brahmana, Aranyaka, Srauta, and Grihya Sutras; the second one with all the texts except Samhita; the third one known only through references in the commentary of Brahmadatta on the Sankhayana; and the last one through a single reference in the commentary of Bhavatrata on Jaiminiya Srautasutra. Thus the existence of manuscripts of Kausitaki Brahmana Upanishad, and Grihya and Srauta sutras belonging to this school indicate the previous existence of Kaushitaki Samhita.