One of the classical hallucinogens of the Americas is the snuff prepared from beans of the leguminous tree Anadenanthera peregrina. (L.) SPEG., better known in the litterature by its former name Piptadenia peregrina (L.) BENTH. In a previous work, specimens of seeds from Puerto Rico were analysed together with an 120 years old material [1]. It was postulated that the relative content of the various alkaloids upon storage follows with time a certain pattern. In order to have a precise idea about those variations, seeds were obtained in 1977 from the same colony of trees in Puerto Rico. Th mature seeds were stored in the laboratory (dark, 20°C). At regular intervals, 2 g. specimens were taken for presevation (dark, -30 0 C) in a sealed glass tube under N2 or Ethanol. The alkaloids were extracted and analysed by GC-MS. Quantitation was performed by HPGC using an electronic integrator and bufotenine as an external standard. Freshly collected seeds contained mostly bufotenine (5-0H-DMT) and Dimethyl- tryptamine, with less N-Methyl-tetra-hydro-~carboline and 5-Methoxy-dimethyl-tryptamine, although seeds kept for more than one year contained 5-0H-DMT only. Pattern of metabolism for each substance will be presented. 1. Schultes R. E., B. Holmstedt, J.-E. Lindgren and L. Rivier: Botanical Museum Leaflets Harvard University 25, 273 (1977).