1. Qualitative and quantitative compositions of the main alkaloids in five development phases of the Goebelia pachycarpa C. A. Mey. have been determined. 2. The radioactivities of the alkaloids isolated after feeding the plant with assumed precursors -[2-14C] lysine and [1,5-14C] cadaverine - show that vigorous synthesis of alkaloids takes place in the flowering and budding periods. 3. The results of an investigation of the oxidation products and of the alkaloids introduced and isolated after the feeding of plants with labelled matrine and labelled sophocarpine show that the alkaloids undergo interconversion without intramolecular changes. © 1978 Plenum Publishing Corporation.