Artemisinin is an important antimalarial drug that is presently being used for controlling the resurgence of malaria. Attempts have been made to partially purify the proteins involved in the bioconversion of arteannuin B to artemisinin by affinity chromatography and precipitation techniques. Our studies indicate that a Tris-HCl buffer system is better than a phosphate buffered saline buffer system. Highest specific activity (0.1 units/mg) with crude cell-free extract has been obtained with this system. A threefold and fivefold increase in specific activity was observed when the proteins were partially purified by acetone precipitation and affinity chromatography, respectively. This is the first report on the study of proteins involved in the bioconversion of arteannuin B to artemisinin.