The tree speciesP. indica (Lauraceae) is an important endemism in the Canary Islands laurel forest and can readily be distinguished by its defoliated appearance due to the seasonal action of wild rats (Rattus rattus), which eat the plant and become intoxicated. These observations and the phytochemical interest of this plant species led us to study the potentially toxic chemicals responsible for such action. We found that an ethanolic extract ofP. indica and its water fraction were toxic when injected into laboratory mice. The mice also died after ingestion of the stems and showed a significant preference for those extracted and rehydrated with an 8% aqueous extract solution when compared with the water control. Two compounds that have been isolated from the toxic fraction and identified by spectroscopic methods are the polyhydroxy pentacyclic diterpenes ryanodol and cinnceylanol. Possible ecological implications are discussed.