Does Gilbert's disease exist?

18 454 men and 5471 women attending a screening centre had serum-bilirubin concentrations measured. 2.0% of men and 0.6% of women had concentrations of 25 micronmol/1 (1-5 MG/DL) or above. Both sexes showed skewed distributions for bilirubin concentration, but analysis of the data showed no evidence of bimodality for either sex. This suggests that people who are now diagnosed as having Gilbert's disease may constitute upper end of the normal range rather than a disease state. The term "constitutional hyperbilirubinaemia" is preferable, and its use can be coupled with reassurance to the patient that the condition causes no symptoms.