In the recent years genetic background of pregnancy induced hypertension (PIH) are intensively investigated. Genetically determined differences in activity of renin-angiotensin system (RAS) are of importance to hypertension susceptibility. The insertion/deletion (I/D) polymorphism of angiotensin I converting enzyme (ACE) was suggested to play an important role in the aetiology of idiopathic hypertension. We have tested if this polymorphism could be associated with PIH. ACE polymorphism was investigated in 87 pregnant women with PIH and in 110 healthy pregnant women (control group). Investigation was performed by polymerase chain reaction (PCR). We have amplified genomic DNA excteracted by phenol-chloroform method from blood leucocytes. We have detected overrepresentation of the I allele in the PIH group (47.2% and 41.4% in PIH and controls, respectively). ACE genotype frequency in control group was in agreement with expected values, according to Hardy-Weinberg law, but in the PIH group the obtained values were different from expected. This observation confirmed the possible role of I allele in aetiology of PIH, and we believe that continuation of this investigation is necessary.