Partial purification and characterization by polyacrylamide gel electrophoresis of human and rodent malate dehyrogenase revealed the presence of two distinct isoenzymes, one associated with the mitochondrial fraction (M‐MDH) and one with the soluble fraction (S‐MDH). Electrophoretic mobilities of the isoenzymes obtained from human and rodent gingiva wre similar. Malate dehyrogenase distribution patterns of the subcellular fractions suggest that the S‐MDH isoenzyme may be more active than the M‐MDH isoenzyme in rodent gingiva. Malate dehydrogenase distribution patterns in mild to moderately inflamed human gingiva were similar to those seen in dilantin hyperplastic gingiva. S‐MDH and M‐MDH isoenzyme distribution patterns could not be fully evaluated because of the high activity of the M‐MDH isoenzyme seen in the soluble fraction. However, the subcellular distribution patterns and electrophoretic mobility in human gingiva showed trends similar to those seen in rodent gingiva. Malate dehydrogenase specific activities in total homogenates of human inflamed and dilantin hyperplastic gingiva were similar.