Chemical availability of calcium was measured with and without simulated digestion to determine processing effects. Available calcium was low in spinach and significantly higher in skim milk and whole milk, consistent with their known bioavailabilities. In nondigested processed milk it was significantly higher for whole milk than for skim milk. However, available calcium in digested whole milk was lower than in digested skim milk. Digestion increased available calcium in skim milk, dialyzable and ionic dialyzable calcium in whole milk and ionic calcium in spinach. Soluble and ionic soluble calcium were lowered in whole milk during digestion due to soap formation. Effects on % calcium were slight, but available calcium in nondigested skim milk was significantly lowered by processing.