Infections with Mycobacterium ovium ssp. paratuberculosis (M. paratuberculosis) are increasingly recognised worldwide. In addition to an increased prevalence of paratuberculosis in Austrian cattle herds, recent years have also shown a rise in infections with M. paratuberculosis in wild red and roe deer, chamois and mouflon. During the period from June 2002 to September 2004, mesenteric lymph nodes were taken from a total of 483 wild animals hunted or found dead and from 338 deceased cattle. Samples were analysed using PCR and cultivation methods. In the case of pathomorphological changes or anamnestic indications, investigations also included an analysis of organ samples (e.g. liver, lung) or foetuses. The tests revealed that 129 wild animal samples (red deer, roe deer, chamois, mouflon, fallow deer, ibex, foxes, mountain hare, yellow-necked field mouse, and capercaillie) contained M. paratuberculosis. The major symptoms in the wild aninodes. Evidence of diarrhoea was only observed in about 15% of the positive cases. The study for the first time provided evidence of intrauterine transmission of M. paratuberculosis in red deer (3 cases) and chamois (1 case) and succeeded in the isolation of the pathogen from the liver, lung and subcutaneous granulomas of wild animals. Of the total of 338 mesenteric lymphnodes of cattle from 303 herds, 80 samples from 77 herds tested positive for paratuberculosis. Twenty-two wild animal and 3 cattle isolates have so far been molecularly typed using IS900-RFLP and RAPD analyses in order to prove epidemiological relationships between occurrences in cattle and wild animals. The increase of paratuberculosis in wild animal species is assumed to have been caused by the purchase of animals, a strong increase in suckler cow farming (cow-calf herds) with a concentration of pathogens in the environment and by inadequate feed hygiene for wild animals.