Publicly financed construction is a keydriver for economic growth and poverty reduction worldwide.At the same time, it is a sector unusually prone tocorruption, not least due to large opportunities for rentextraction and the technical complexity of infrastructureinvestments. Transparency international's bribepayer's index ranks construction as the sector mostlikely to bribe public officials and seek state capture, andan estimated 10-30 percent of the US$5 trillion spentannually on construction worldwide is lost to corruption.Guatemala joined Construction Sector Transparency Initiative(CoST) as an associate country with support from the WorldBank in November 2009. As such, it differed from pilotcountries in two respects. As CoST Guatemala moves frompilot to expansion in July 2011, it is hoped that theaforementioned success factors will allow the initiative toamplify this effect-and further enhance transparency in asector so crucial to the country's development.