1. An NADP-specific glutamate dehydrogenase (E.C. 184.108.40.206) of mitochondrial origin has been detected in M. senile, a sea anemone. 2. Substrate specificity and starch gel electrophoresis experiments indicated an absence of the NAD(P) glutamate dehydrogenase (E.C. 220.127.116.11). 3. This NADP specific GDH activity appears to be the sole GDH activity in species of the animal phylum Coelenterata.