Fourteen farmed hares were inoculated intranasally with a bacteria-free liver suspension of a hare, which had died of EBHS. Following an incubation period of 24-72 h 7 of these animals reacted with a rise in rectal temperature of greater-than-or-equal-to 1.0-degrees-C reaching 40.7 to 41.1-degrees-C. Except for one hare the rise in temperature lasted for only 24-48 h. In 2 cases a premortal drop in temperature was observed. Likewise 7 hares showed a distinct increase in the activity of the liver-dependent enzymes AST (GOT), ALT (GPT), LDH, alkaline phosphatase (AP), gamma-GT and GLDH. On account of the increase in body temperature as well as enzyme activity the index of infection is assumed to be approximately 0.5. Two animals succumbed (one on the 3rd, the other one on the 4th day p. i.), 2 other hares were euthanized on day 3 p. i. in poor condition, indicating a peracute to acute course of the disease. On pathomorphological examination the above-mentioned 4 animals exhibited a light brown liver with prominent lobules and reduced consistence, occasionally with haemorrhages; moreover moderate hyperaemic splenomegaly was seen. Histological examination of the liver showed hyperaemia, single-cell-, group- and mass-necrosis as well as panlobular fatty degeneration. Other animals, which were euthanatized during the course of the experiment (2 of them younger than 2 months) did not show any pathological alterations indicative of EBHS. In liver and to some extent spleen homogenates of the 4 hares with noticeable pathological results, viral haemagglutinin could be demonstrated with titers up to 1:16384 using human group "0" erythrocytes. An acid buffer was required for detecting EBHS-antigen, in our laboratory PBS of pH 6.0 with 20 % gelatine added proved to be optimal. By means of electron microscopy in liver homogenates numerous non-enveloped icosahedral virus particles, 34-37 nm in diameter and with cup-shaped depressions on the surface could be demonstrated. The virions showed the same morphology as those of Rabbit Haemorrhagic Disease (RHD). Using HI-test all of the infected hares exhibited seroconversion. With the homologous EBHS-antigen the antibody titre was 4.8 times higher than with RHD-antigen.