This thesis examines the rise and decline of the York Buildings Company, one of the many joint-stock companies involved in the speculative fever in London in 1720. The company's books do not appear to have survived and this circumstance has meant that its affairs have been reconstructed from legal records, parliamentaryreports, family papers of participants and contemporary pamphlets and newspapers as well as secondary sources. The fact that sufficient information was derived from contemporary sources to produce a full-length case study is a fair indication of its importance to contemporary businessmen. The company's origins as a supplier of water in seventeenth and eighteenth century London and the technology it employed are examined. An oversight by Parliament granting the company unlimited landholding powers paved the way for it to acquire estates forfeited after the 1725 Jacobite Rebellion allowing speculators to reorganise it as a financial and commercial concern. Its affair s are investigated in the context of the business world of the eighteenth century revealing much corruption both within and without the company. Participants are linked to other dubious and fraudulent projects suggesting that several joint-stock companies operating in London were controlled by a relatively small group of individuals. This view is reinforced by case studies of the Charitable Corporation and the Harburgh Company which show close links with and frauds similar to that of the York Buildings Company. The conduct of individuals connected with the company also reveals much about the business and political morality of the age. The complex nature of the company's organisation, particularly in landowning and industry confirms that a lack of suitably qualified managers was an important contributory factor to the company's problems. Parliament was ineffective in its attempts to regulate the affairs of the York Buildings Company, a circumstance partly explained by the corruption in public life, so frequently the subject of comment.