SUMMARY1. An account is given of the preparation and a few of the properties of a compound isolated from the extracts of Sumatra‐type derris root.2. This compound although in the present investigation containing extraneous material, probably sumatrol, yields optically inactive toxi‐carol in high yield, and is characterized by the switch‐over from laevo‐to dextro‐rotation on the addition of caustic potash in methyl alcohol to its benzene solution. and is mainly responsible for this feature of the Sumatra‐type resins under similar treatment. The change‐over in rotation was followed by a gradual fall in rotation of a unimolecular type. The compound is laevo‐rotatory in benzene and dextro‐rotatory in alcohol.3. The toxicities toAphis rumicisof rotenone, toxicarol precursor, sumatrol, toxicarol and the residual resins from the Sumatra‐type andDerris ellipticuroots have been determined. In our experiments the toxicity in descending order was Rotenone>D. ellipticaresin>Sumatra‐type resin>sumatrol = toxicarol precursor>inactive toxicarol.4. The statistical method used in analysing the insecticidal data is des