This article reports developments in the west Pannonian population of Great Bustard between the years 1900 and 2008/2009. Recent population numbers were acquired by regular monitoring activity at seven main study sites; historic numbers are based on the available literature and in some cases on estimates. Of the seven main areas currently studied, three are in Lower Austria (Westliches Weinviertel, Marchfeld and Rauchenwarther Platte) and two in the north of Burgenland (Parndorfer Platte and Hanság). A sixth study area (Heideboden) is at the intersection of three countries and is made up of areas in northern Burgenland, Hungary and Slovakia. The final study site (Mosonszolnok) lies mostly within Hungary, with some areas in northern Burgenland. The west Pannonian population of Great Bustard showed a marked decline in numbers from a total of at least 3,500 individuals in 1900 to about 130 in 1995. Factors implicated in the decline are changes in habitat, resulting largely from agricultural transformations and the development of human infrastructure, as well as hunting pressure. As a result of intensive trans-border protetion measures the population recovered from the low in 1996 to at least 376 individuals in the winter of 2008/2009. The Austrian Great Bustard population declined from a total of 700–800 individuals around the middle of the 20th century to a low of about 60 individuals at the end of the century. By the breeding season of 2008 it had increased again to 210 individuals. Remarkably, population trends differed in the different study areas. On the Rauchenwarther Platte the breeding population became extinct by the breeding season of 2005. In Marchfeld there was a huge decline in the population between 1990 and 2006 followed by a slight increase in the breeding population since then. On the Hanság the population has remained more or less stable since 1990. On the Parndorfer Platte there has been an increase in the population since 2007 and in the Austrian part of the Heideboden as well as in the Westliches Weinviertel there has been a huge increase from as long ago as 1998. There have been steep declines in populations in the breeding season between 1940 and 1996 in western Hungary as well as in eastern Austria. Since then both populations have been recovering, with numbers in eastern Austria increasing even more than in western Hungary. The results show that Great Bustard subpopulations within the west Pannonian Population are in exchange, that population trends clearly depend on the availability of conservation plots and that smaller and temporarily abandoned areas may be resettled by immigration from well reproducing subpopulations.