Calcium and phytate phosphorus were highly soluble below pH 4 at all molar ratios of calcium (Ca) to phytic acid (PA) studied (0.512.67). As pH is increased above 4, there is a drop in solubility, the magnitude of which depends on the Ca:PA molar ratio. Above pH 6, the greatest calcium precipitation occurred at molar ratios between 4 and 6.5; both lower and higher Ca:PA molar ratios showed higher calcium solubility. In contrast, phytate phosphorus solubility decreased in proportion to the Ca:PA molar ratio, showing essentially complete precipitation above the Ca:PA ratio of 5. The pentacalcium phytate salt probably predominates when calcium is not limiting. Under calcium-limiting conditions, the complexes resolubilize as the pH is increased above 7.