Rotor syndrome is a rare familial conjugated hyperbilirubinaemia with notmal liver histology and unknown cause. The hypothesis was tested that it can be an allele variant of Dubin-Johnson syndrome, caused by mutation in ABCC2 gene. The ABCC2 gene and protein were investigated in two patients with this syndrome. No sequence variations were found in 32 exons, adjacent intronic regions and the promoter region of ABCC2. Accordingly, Rotor syndrome is not an allelic variant of ABCC2 deficiency.