In 2006, with David Kilgour he released the Kilgour-Matas report, which stated "the source of 41,500 transplants for the six year period 2000 to 2005 is unexplained" and "we believe that there has been and continues today to be large scale organ seizures from unwilling Falun Gong practitioners". In 2009, they published an updated version of the report as a book. They traveled to about 50 countries to raise awareness of the situation. Later Matas stated, "We estimate in the period between 2000 and 2005, there were 41,500 transplants which have no other explained source".