The fundamental idea behind a PPP is not new. Private firms have been involved in delivering public services for decades in a variety of configurations. Since the 1980s, however, different PPP modalities have acquired distinct characteristics as experience has been gained in delivering a broader range of public goods and services, and partnering across multiple project stages, such as building, financing, and operation and maintenance. PPPs are being increasingly used in Asia, but the level is still quite low compared with developed countries. While the risk-sharing characteristic of PPPs makes this modality more attractive than traditional procurement, the complexity of PPPs is an obstacle to these partnerships.