Hyperhomocysteinaemia, a risk factor for recurrent pregnancy loss, is related either to a hereditary defect within the methionine-homocysteine pathway or it might be acquired as a result of deficiencies of vitamin B(12) and folate (B(9)). Because hyperhomocysteinaemia seems to be determined by both genetic and environmental factors, the current study was undertaken to find out the interactions between folate status and MTHFR mutation on the homocysteine concentration in 24 women experiencing unexplained three or more consecutive recurrent pregnancy losses. The median fasting total plasma homocysteine concentration in the study group was 10.23 micro mol/l compared to 8.95 micro mol/l; P = 0.096 in the controls. Elevated homocysteine levels > 18 micro mol/l, which was considered to be a risk factor for recurrent early pregnancy loss, was found in four women in the study group and none among the controls. Lower red cell folate levels (normal range >/= 160 ng/ml) were observed in nine (37.5%) women among the study group, compared to five (20.84%) women among controls. The mean +/- SD red cell folate levels in the study group was found to be 154.37 +/- 37.07, while in the controls it was 159.0 +/- 28.97. In the present study six women in the study group and two among controls were found to be carriers for the C677T MTHFR mutation. None were homozygous for the mutant (TT) allele. The highest values of homocysteine concentration were found in women experiencing recurrent pregnancy loss with both the CT genotype and folate deficiency. Identification of hyperhomocysteinaemia in women with recurrent pregnancy loss may help in therapeutic normalisation and might permit a normal birth.