The extraction power of supercritical carbon dioxide and nitrous oxide for pure alkaloids, their salts, and their corresponding medicinal plants was examined. The main alkaloids of the following plants were selected : Areca, China, Colchicum, Qonium, Ephedra, Ipecacuanha, Nicotiana, Opium, Rauwolfia, Atropa and Catharanthus. The test were done with a micro extraction apparatus coupled directly with TLC, mainly m the pressure region between 80 and 200 bar, at a temperature of 40° Celsius. The results show a relation between extractability and constitution of the alkaloids. Supercritical carbon dioxide has a good extraction power for certain alkaloids; in comparison to this, fluid nitrous oxide, however, proves to be superior.