This thesis is a study of the K__yapaparivarta, an early Mah_y_na s_tra which was translated into Chinese between as early as the second and tenth centuries. It has two related goals: to investigate the textual history of the K__yapaparivarta by examining various versions that have been preserved in Sanskrit manuscripts, Chinese and Tibetan translations; and to study the stylistic features of the Sanskrit version of the K__yapaparivarta to see if they can tell us about the method of the composition of Mah_y_na s_tras. My central argument is that Mah_y_na s_tras were composed in written form which is different from the early Buddhist texts that were composed orally. However, the oral/aural tradition was still the primary concern of Mah_y_na composers. I start with the investigation of all extant versions of the K__yapaparivarta to illustrate the picture of the popularity of this text. Then, I compare all versions by using the methodology of textual criticism. I propose that the K__yapaparivarta has three stages of development: the early stage, the middle stage, and the final stage. Each stage shows some changes to the text in terms of structure, wording, and length. I propose that this variation might be the effect of writing that was used in the composition and transmission of Mah_y_na s_tras. In the second part of this thesis, I examine the stylistic features of the Sanskrit version of the K__yapaparivarta. I begin with the investigation of the theory that Mah_y_na s_tras were composed in written form. I argue that although Mah_y_na s_tras may have been composed in written form, the oral/aural tradition was still the central concern of Mah_y_na authors. I then examine the stylistic features of the text to find out to what extent the oral/aural tradition influenced the composition and transmission of the K__yapaparivarta. By analyzing the stylistic features, I conclude that the significance of the oral/aural culture never decreased in Mah_y_na Buddhism. Most of the stylistic features were modeled on the early Buddhis texts. However, the inconsistency and the innovation of some stylistic features of the K__yapaparivarta might indeed suggest that it was composed in written form.