From 1995 to 1997 the prevalence of serum antibodies against Mycobacterium avium subspecies paratuberculosis (M. av. ssp. pt.)- the causal agent of paratuberculosis (Johne's Disease) - was examined in 11,028 Austria cattle. Samples of the 4 oldest cattle of 2,757 farms were collected according to a specific sampling schedule for this epidemiological study. District, age and breed of animals were included in this study. For antibody screening against M. avium subspecies paratuberculosis a modified, commercially available ELISA (ALLIED Monitors, Fayette, USA) was employed. 2,253 samples that were found to be positive or questionable were subjected to further testing with a more specific ELISA (Institute of Microbiology and Infectious Animal Diseases). Results of this study were used for statistical analysis. Average prevalence of antibodies to M. avium subspecies paratuberculosis was 1.99 % in Austria. Highest prevalence was seen in 6 year old cattle (2.84 %) and Holstein Frisian cattle (3.51 %).Seropositive animals were found in 6.96 % of farms tested, and prevalence was highest in Vorarlberg, followed by Salzburg, the Tyrol, Styria and Carinthia. This study is unique in Europe in the use of an adequate random sampling plan for an investigation of this magnitude.