The present invention relates to zofenopril calcium form A substantially free of other forms of zofenopril calcium and to zofenopril calcium having a chemical purity of more than 98.5%. The present invention also relates to methods of preparing such zofenopril calcium. It further relates to compositions comprising such zofenopril calcium. Zofenopril calcium, (4S)-1-[(2S)-3-benzoylthio-2-methylpropionyl]-4-(phenylthio)-L-proline calcium salt, has the following structure: