Jack Kerouac's spontaneous prose method was inspired in part by his use of drugs while writing. While there is abundant biographical evidence that Kerouac used drugs frequently, little attention has been paid to their effects on the development of his style. This thesis attempts to demonstrate that the altered states of consciousness produced by Kerouac's drug use should be considered in conjunction with historical, cultural, and biographical forces in tracing the evolution of Kerouac's creative growth. As a member of the Beat Generation, Kerouac used drugs both as a social statement of rebellion and for artistic insight. In fact, he consciously entered into a well-established tradition of writers looking to drugs as modern-day muses. Within this legacy, drugs were commonly viewed as chemical gateways to a transcendental realm of visionary truth that the artists could enter and return with, thus becoming a literary seer. Kerouac, who believed that the ossification of standardized written English into rigid forms of grammar and sentence construction curtailed its potential for complete communication, sought a prose style that would allow for a maximum of authenticity and fidelity to organic thought with a minimum of revision. Kerouac used drugs like amphetamine, marijuana, and alcohol, each of which offered unique modes of perception, to enter into new frameworks of consciousness, and then recreated these altered states in writing. These three substances—amphetamine, marijuana, and alcohol—served as the basis in the development of Kerouac's style. Amphetamine, in the form of the over-the-counter drug Benzedrine, gave Kerouac the energy for his legendary typing marathons, allowing him to write On the Road in three weeks and The Subterraneans in three days. While writing On the Road in particular, Kerouac began formulating the stylistic approach that he subsequently dubbed "spontaneous prose." Its basic tenants, including a de-emphasis on revision, limited punctuation, and long sentences, were encouraged by Benzedrine's stimulant properties, which tended to focus Kerouac's attention on the exterior world of events, temporality, and movement. His amphetamine-induced texts attempt to communicate accurately by confessing the minutia of surface details. Kerouac's spontaneous style, however, soon evolved into the "sketching" technique seen in Visions of Cody and Dr. Sax, partially as a result of his marijuana-induced desire to share subjective perceptions truthfully. Rather than focusing on the exterior world, the marijuana texts look inward for authenticity. Marijuana helped Kerouac facilitate this inner orientation by its pharmacodynamic tendency to induce dream-like, associative states; when reproduced textually, these impressions seemed to resemble the unconscious structures of Kerouac's mind, which he shared hoping for complete communication via the universality of shared experience. Kerouac used both the amphetamine and marijuana modes to varying degrees and interchangeably for most of his career, and with the first section of Desolation Angels, written in sobriety, achieved their greatest synthesis, demonstrating that drugs were not the props to his style, but rather the impetus—even in the absence of drugs, Kerouac's prose retained its own essential, idiosyncratic features. Finally, in the latter part of Kerouac's career, alcohol proved that drugs could also negatively affect his style, as shown in Big Sur and Vanity of Duluoz. Their return to a plainer prose—some would say poorer prose—was no doubt the result of rampant alcohol abuse, and the unfortunate end to Kerouac's life and writing.