We experienced two cases of Rotor syndrome in brothers who were a 13 year-old boy and an 11 year-old boy, respectively. They presented with icteric scleras for a few months. Their common laboratory characteristics were as follows: Direct bilirubin was more increased than indirect bilirubin, but aminotransferases were normal. Plasma indocyanine green (ICG) test revealed hepatic excretory defect: plasma ICG concentrations 15 minutes after intravenous injection were 80.45% and 78.28%, respectively. 99mTc-DISIDA Hepatobiliary scan showed that severely decreased hepatic extraction with mild cardiac blood pool, markedly delayed biliary excretion in both intra- & extra- hepatic bile ducts, delayed visualization of gall bladder, and markedly delayed intestinal biliary passage. Needle liver biopsy showed normal hepatic histology without pigmentation.