Since the 1990’s, public-private partnerships agreements (PPPs) have been used as a main tool for investments in public infrastructures. The movement began in the United Kingdom and fortunately became a great success, which later was adopted by many other countries in Europe, Asia and the Americas. As international experiences have shown, the combination of private capital in public services and facilities can be very thriving, particularly under the best value for money principle. In an overall approach, this study compares the UK (original) PPPs with the newly Brazilian PPPs, focusing on the financial contractual risks under both systems. The analysis shall emphasise the mandatory financial contractual guarantees given by the public sector to the private sector, within the Brazilian PPP legal framework (Federal Law nº 11.079/2004, article 8). Therefore, this book should help clear some basic definitions and understandings on both systems and should be especially useful to professionals on public and private initiatives, either supplying, financing or contracting under PPP agreements.