Umbilical artery blood velocity A/B ratios were recorded in term fetuses once before and twice after the maternal epidural injection of either 8 ml of lignocaine plain (15 women) or lignocaine with adrenaline 1:200,000 (40 micrograms) (16 women). The administration of lignocaine plain led to decreases in the ratio of varying degrees in all fetuses regardless of the height of the initial A/B ratio. The injection of lignocaine with adrenaline produced identical results in fetuses with initially normal A/B ratios. In contrast, all six fetuses with initially high A/B ratios (above 2.90) who received the adrenaline-containing anaesthetic reacted with a rise in the ratio, and two of these developed transient heart rate decelerations. Thus, if the initial resistance in umbilical blood flow is high, even the small epidural dose of 40 micrograms of adrenaline produces a further increase which may be associated with clinical implications.