Abstract 1. 1. A high affinity Ca 2+ binding and low mol. wt protein, parvalbumin, was purified from monkey skeletal muscle. 2. 2. As compared with other animals, only one component and a lower content of monkey parvalbumin were found. 3. 3. This may suggest that both the component and the content of parvalbumin decreases with biological evolution. 4. 4. The parvalbumin was found to have a mol. wt of 11,400, a pI of 5.1, a high aspartic acid and lysine content, maximum absorption at around 260nm, a blocked amino-terminal, an immunological distinction, 2 mol Ca 2+ binding/mol, and a conformational change by Ca 2+ binding. 5. 5. Parvalbumin was shown to have alpha type properties.