Five cases of acute fatty liver of pregnancy are described. These are the only recognized cases of this disorder occurring in a 2 year period in Western Australia. Clinical and laboratory features are presented. There was no maternal death. Of the six babies, there were three intrauterine deaths, including the only set of twins. All the babies were male. Vomiting in the third trimester was the chief presenting feature in all cases, often accompanied by a systemic illness with malaise and tiredness. Extreme polydipsia was noted as a prominent symptom in all cases. The combination of moderately abnormal liver function tests, extreme leucocytosis with other blood film abnormalities, hypoglycaemia, impaired renal function, coagulopathy and gross elevation of uric acid level is regarded as highly suggestive of the diagnosis. Features of a preeclamptic illness were present in several cases. Three of the patients have since had uneventful pregnancies. The constellation of clinical and laboratory features is sufficiently characteristic to allow accurate clinical diagnosis in most cases of this disorder. The chances of both maternal and fetal survival are enhanced by early diagnosis allowing intervention in the form of prompt delivery of the infant.