The mitochondrial and glyoxysomal citrate synthase (EC 4.1.3.7) from the endosperm of germinating castor beans (Ricinus communisL., type Sanzibaricnsis) were purified to a final specific activity of 76 and 78 U (mg protein)−1, respectively. Both citrate synthases could be bound to ATP‐Sepharose. However, only the mitochondrial enzyme could be eluted by either 100 μMoxaloacetate or 100 μMcoenzyme A (indicative of affinity chromatography), while the glyoxysomal enzyme was only eluted by 0.5MKCI (indicative of ion‐exchange chromatography). Many properties of the two isoenzymes were similar including the pH dependence and temperature dependence of activity, the pH stability, and the inactivation of the enzyme at elevated temperatures. The most pronounced differences between the two citrate synthases were the isolelectric points of pH 5.9 for the mitochondrial and of pH 9.1 for the glyoxysomal enzyme. Both citrate synthases are dimers in the native form with a molecular weight of 95000 each, as determined by gel filtration on Sepharose CL‐6B and by polyacrylamide gel electrophoresis in the presence of 0.1% sodium dodecyl sulfate. However, the glyoxysomal citrate synthase existed also as a tetramer with a molecular weight of 200000 in the presence of 1