Chloritoid and staurolite stabilities have been analyzed as functions of total pressure, partial pressure of oxygen, and temperature. At 10 kb, in the upper part of the magnetite field, the equilibrium relations among chloritoid, staurolite, almandine, and others, are dependent upon oxygen pressure. The staurolite field is a restricted triangle within this isobaric plane and is likely to pinch out gradually with increasing pressure. In the upper part of the magnetite field, almandine breaks down to assemblages involving respectively chloritoid, staurolite, and kyanite, in order of increasing temperature. Staurolite in natural processes is discussed; the isograds of staurolite-quartz, and kyanite-muscovite-quartz do not have significance in oxidizing environments.