Common ragweed (Ambrosia artemisiifolia) is an invasive alien species indigenous to North America. Ragweed is a big threat to agriculture and has a serious impact on human health. The most important area with ragweed occurrence within Europe is Pannonian Plain in Central Europe. This research introduces for the first time the unique, direct broad-scale survey of A. artemisiifolia in relation to real-life occurrence and infestation in the field. To understand the distribution of ragweed in the territory the geospatial analysis was applied to create 2D map in ArcGIS environment. The field survey was undertaken during summer 2014 in the Žitný ostrov (Slovakia). The investigation revealed that spatial occurrence of A. artemisiifolia is not homogeneous and there is also striking territorial heterogeneity of infestation rate. Ragweed was observed at 80 (47.2%) out of 169 sites. The infestation of arable land (mostly stubbles) varied from weak infestation, 24 sites (1-30 plants*10 m -2 ) to heavy infestation, 26 sites (˃80 plants*10 m -2 ). The research on associated plant communities was also carried out. Stubble field's vegetation was found to be highly species poor, on an average only 2.5 species*10 m -2 . Among 40 recorded species the most frequent (noticed at 25% sites) were Datura stramonium, Chenopodium album, and Mercurialis annua. This broad-scale survey provides an overview and useful information on considerations needed to make decisions about ragweed control and potential future expansion. The presented study offers also inventory of ragweed frequency over the large area. . Spomedzi 40 zaznamenaných druhov patrili k najčastejším (zaznamenaným na 25% lokalitách) Datura stramonium, Chenopodium album a Mercurialis annua. Tento plošne rozsiahly prieskum poskytuje celkový pohľad a užitočné informácie potrebné k rozhodnutiam dôležitým pre reguláciu ambrózie a o potenciále ďalšieho šírenia. Predkladaná štúdia katalogizuje aj výskyt ambrózie na veľkej ploche.