The endoparasite fauna of 108 sika deer (42 calves 1 year) originating from the two free-living sika deer populations in Austria (Ostrong, 35 animals; Tullner Donauauen, 73 animals) was studied. The deer were shot during the hunting seasons 2003-2005. In all, at least four species of protozoa (Eimeria austriaca, Eimeria robusta, Eimeria sordida; Sarcocystis spp.), two species each of cestodes (Moniezia benedeni, larval cyst of Taenia hydatigena) and trematodes (Dicrocoelium chinensis?, Fasciola hepatica) and 16 species of nematodes were identified including 14 species recovered from the gastro-intestinal tracts and one species each isolated from the lungs (Dictyocaulus eckerti) and the abdominal cavity (Setaria cervi). Endoparasites were recovered from all 108 deer with prevalences of 44% for Sarcocystis spp., 14.8% for Eimeria spp., 4.6% for Fasciola hepatica, 27.6% for Dicrocoelium chinensis?, 3.1% for Dictyocaulus eckerti, 3.7% for Moniezia benedeni and 98.1% for gastro-intestinal nematodes. The burden of gastro-intestinal nematodes ranged from zero to 1089 with a geometric mean of 149 worms. The abomasums, small and large intestines harboured 81%, 14% and 5% of the total gastro-intestinal nematode burden. Spiculopteragia houdemeri (93.5%), Oesophagostomum sikae (87.9%), Oesophagostomum venulosum (51.4%), Cooperia pectinata (42.1%), Spiculopteragia böhmi (23.4%) and Ostertagia leptospicularis (16.8%) were the most prevalent nematode species of the gastro-intestinal tracts. Spiculopteragia houdemeri and Rinadia andreevae were new records for Austria.