Objective      To determine the correlation of Gilbert syndrome (GS) and UGT1A1 variations.       Methods      The genome DNA was extracted from the peripheral blood samples of 8 probands (subjected in our outpatient department from August 2011 to March 2014) and their family members. The promoter and coding regions of UGT1A1 were amplified by polymerase chain reaction (PCR). The amplified DNA fragments was sequenced and then family pedigree analysis was analyzed. Bilirubin levels of all probands were followed up for at least 1 year.       Results      The incidence of GS was only 25% (less than 50%) among the probands’ parents in the 6 complete nuclear families. The twin brother of a proband was also a GS patient. Only one brother of the proband was affected in other 3 families in which the probands had a brother or sister. Only a sister was detected with unconjugated hyperbilirubinemia in 4 sisters of the second generations. Three missense variants in coding regions (c.211GA

p.G71R in exon 1; c.686CA

p.P229Q in exon 1; c.1091CT

P364L in exon 4）and 2 extra bases insertion variant in promoter (c.-40_-39insTA) were identified. Twelve of 15 affected subjects carried homozygous or compound heterozygous variations which contained at least 2 unlinked variants (0.80) and the other 3 carried single UGT1A1 heterozygous variations

while 13 of 14 family members carrying single heterozygous variations kept normal bilirubin levels.       Conclusion      GS is strongly associated with UGT1A1 variations in an additive effect. Those carrying homozygous or compound unlinked heterozygous UGT1A1 variations (c.-40_-39insTA/c.211GA; c.211GA/c.1091CT) are more common suffering from GS

while those carrying single heterozygous variations are healthy.