Triggered by a case of ischaemic hepatitis (shock liver) in a patient with severe respiratory insufficiency, we tried to gather information about clinical characteristics and incidence. To our surprise, this information could be found neither in major critical care, medical or gastroenterology textbooks nor in textbook indices or works on differential diagnosis. From Sept. 1989 to May 1990 we studied all possible cases of ischaemic hepatitis in a 390 bed general hospital, to establish incidence. Using computerised data from the clinical chemistry laboratory, all patients with grossly abnormal liver function tests were identified. In this nine-month period 27 adult patients had a peak ALAT level of > 500 U/l: 8 of these suffered from ischaemic hepatitis, using the criteria described by Gibson et al. In another 5 this diagnosis was suspected but could not be ascertained before death (30% and 18% of all cases). In all these cases ASAT, ALAT, LDH levels were 8-100 times normal, but bilirubin, alkaline phosphatase, gamma-glutamyl transferase and prothrombin time were only slightly abnormal. With correction of the underlying disorder enzyme levels returned to normal very rapidly, in 5-10 days. Ischaemic hepatitis could easily be distinguished from other causes such as alcoholic, viral or drug-induced hepatitis. Ischaemic hepatitis was the most frequent cause of severely elevated ASAT, ALAT and LDH in hospitalised patients. The diagnosis can easily be made on clinical characteristics and the typical biochemical pattern. An elaborate work-up or invasive procedure is redundant. Prognosis per se is excellent but depends on the underlying disorder.