Summary: Between 1965 and 1984, 139 pregnancies in 125 women were complicated by obstetric cholestasis (OC). Prevalence increased from 0.1% in the first 10-year period to 0.2% in the second (p< 0.001), following recognition of the adverse fetal risks of this condition. Perinatal data from both series, 1965–1974 and 1975–1984 have previously been published. Mothers in the latter series were more likely to be of Anglosaxon than Mediterranean origin (p< 0.001) and did not have underlying haemolytic conditions. Diagnostic criteria changed considerably over the 20 years, such that liver biopsy was no longer needed, gastroenterological consultation was sought less frequently (p< 0.001) and newer diagnostic criteria of increased bile acids with negative hepatitis serology were increasingly employed. Biochemical data were broadly similar in the 2 groups. An understanding of the clinical and laboratory features of this disease facilitates early diagnosis, which is imperative if intensive fetal surveillance is to reduce the high stillbirth rate in OC.