The HELLP syndrome has been associated with postpartum unconjugated hyperbilirubinaemia. Several types of disorders cause unconjugated hyperbilirubinaemia, Gilbert's syndrome being the most common. In Caucasians a genetic defect in the TATA box of the promotor region of the gene encoding for bilirubin UDP-glucuronyltransferase is tightly associated with Gilbert's syndrome. This defect was assessed by polymerase chain reaction in 237 women with the HELLP syndrome in their obstetric history and 236 controls. Fifteen percent of the cases and 10% of the controls had a homozygous genetic defect (chi2 = 2.9; P = 0.23). No evidence was found that Gilbert's syndrome is associated with the HELLP syndrome.