The vitamin B1, B2 and B6 status was investigated in a group of rural and urban pregnant women in the northeast of Thailand during the course of pregnancy. The vitamin status of all three vitamins did not change during the course of pregnancy even for the group of rural women. Differences between the group of village women and those females from a high socio-economic urban fraction of the population were only observed for the vitamin B2 status. The B2-dependent enzyme activation coefficient varies between 46.5 up to 56.7% for the rural and between 8.9 to 18.5% for the urban women. Vitamin B6 deficiencies as measured by the activation coefficient varied above 30% up to 40% and more for both groups of women. A functional significance could only be established for vitamin B2 deficiency. The increase of the activation coefficient correlated with an increase in the serum concentration levels of transferrin. Transferrin in turn was inversely correlated with haemoglobin.