Inborn errors of primary bile acid (BA) synthesis are genetic cholestatic disorders leading to accumulation of atypical BA with deficiency of normal BA. Unless treated with primary BA, chronic liver disease usually progresses to cirrhosis and liver failure before adulthood. We sought to determine the prevalence of 2 common disorders, 3β-hydroxy-Δ-C27-steroid dehydrogenase (3β-HSD) and Δ-3-oxosteroid-5β-reductase (Δ-3-oxoR) deficiencies and to describe current diagnostic and treatment strategies among different European paediatric hepatology centres.