By investigating Chinese translations of Buddhist scriptures and the old catalogues, we can trace the transition of titles of Mahāyāna sutras from *vevulla to vaitulya, and then to vaipulya and finally to mahāyānasūtra. In a collection of vaitulya-cum-mahāyāna-scriptures, *Mahāvaitulya-Mahāsannipāta by name, we find sentences which reveal composers of the vaitulya-scriptures were Mahāsāṃghikas. On the other hand, several facts indicate that the Sarvāstivāda school originally did not accept Mahāyāna Buddhism, e.g. the Abhidharma texts of this school never refer to Mahāyāna sūtras. I assume that members of the Mahāsāṃghikas composed new scriptures, often consisting of questions and answers, condemning the conservative thoughts on Buddhist doctrines and called these newly-composed texts vedulla / vaitulya, meaning that they were “irregular” as Buddha’s scriptures but “incomparable, peerless”. Later, they came to be called, in a more positive way, vaipulya “fullness”. Much later still, they came to be called mahāyāna-sūtra as well. As time went by, and these Mahāyāna scriptures and doctrines became much more popular, members of other schools began to acknowledge and absorb them as well. I assume, further, that the original background of the Madhyamaka school might have been the Mahāsāṃghikas, while that of the Yogācāra school may have been the Sarvāstivādins.