Experiments were carried out to see the influence of the infusion and extracts of Symphytum officinale L leaves on the contraction of the isolated guinea oig uterus. The size of the contraction caused by the infusion and extracts were compared to the contraction by Syntocinon injection. A modification of the H.J. Wilkens and F. Sieger method was used to determine the potency. - The infusion and extraction had a stimulating effect on the guinea pig isolated uterus. - The active principle is probably found in the fraction soluble in polar solvents. There is a dose effect relationship. - 3055' infusion is more potent to the fraction soluble in polar solvent (fraction I,IV,V) and is more potent than the fraction soluble in non polar solvent (fraction 11,111). The potency of the 30%.infusion and 0,02 unit of Syntocinon are almost equal The fraction soluble, in polar solvent increased- the contrac tion of the isolated uterus,which urge an investigation o the influence of the plant on pregnant animals to know the abortive effect.