In sheep fetuses 110–130 days of age acidosis (blood pH 6.95; produced by infusion with 1.1 M lactic acid) significantly lowered blood flow (ml/min/100 g) to the full thickness wall of the jejunum from 135 ± 11 to 93 ± 14 and in the full thickness wall of the ileum from 122 ± 13 to 95 ± 11. The decrease was mainly due to the decline in blood flow to mucosa of the segment, where flow decreased from 182 ± 20 to 83 ± 14 in the jejunum and from 130 ± 10 to 107 ± 9 in the ileum. Fetal hypoxemia (PaO₂ of 14.9 mm Hg; induced by allowing ewes to breath 11.1% O₂ and 88.9 % nitrogen) reduced blood flow only to the jejunal mucosa from 142 ± 14 to 99 ± 16. The reduction in blood flow to the full thickness wall of the jejunum and the ileum did not change significantly from the control period, when PaO₂ was 25 mm Hg.