Calcium-binding protein (CaBP) has been isolated from baboon (Papio cynocephalus) intestinal mucosa by gel filtration and ion-exchange chromatography. 2. Similarity in electrophoretic behavior, size and charge and immunologic structure are demonstrated between the baboon CaBP and CaBPs isolated from other species. 3. Baboon intestinal CaBP is resistant to neuraminidase digestion.