To investigate the contribution of the estrogen receptor alpha (ERalpha) polymorphism in the development of obstetric cholestasis and to determine whether multidrug resistance 3 (MDR3) gene 1712delT mutation detected in French patients is also present in Finnish women with obstetric cholestasis.In a retrospective case-control study, two ERalpha polymorphisms and MDR3 gene mutation 1712delT were investigated in healthy control women (N=47) and in women with diagnosis of obstetric cholestasis (N=57). PvuII and XbaI polymorphisms in ERalpha gene were evaluated in genomic DNA by using the polymerase chain reaction (PCR). In addition, the frequencies in the general population in our area are presented for comparison.None of the ERalpha genotypes or alleles was significantly over-represented in obstetric cholestasis. When the two ERalpha gene polymorphisms were analyzed in parallel, six genotype combinations were recognized, and the distribution of these genotype combinations did not reveal statistically significant differences between the cases and controls (P=0.612). No patient or control was heterozygous or homozygous for the mutant allele in the MDR3 gene.The present data indicate that polymorphism of the ERalpha and MDR3 genes 1712delT mutation are unlikely to play any significant role in obstetric cholestasis in affected Finnish women. Further work to identify explanatory factors is of particular interest.