Cell fractionation of Plasmodium lophurae was performed after breaking malaria parasites with a French pressure cell. Cytochrome oxidase activity was used as a marker for mitochondria and most of the mitochondria were located in the 15,500 xg pellet. Serinehydroxymethyltransferase (SHMT) was partially purified from P. lophurae by ammonium sulfate precipitation. The enzyme had a molecular weight of 60,000. In contrast, SHMT from the host liver had a higher molecular weight, 81,000. Studies are continuing on the cellular location of SHMT, further purification of SHMT, the enzyme kinetics of SHMT, and the role of SHMT in the metabolism of malarial parasites.