When skim milk was passed through a column of Sephadex G-150 and eluted with distilled water, it separated into three peaks containing (I) "primary micelle", (II) "whey proteins", and (III) free electrolytes and other small molecules. "Primary micelle" which is composed of calcium caseinate and bound calcium phosphate was compared with whole micelle and colloidal phosphate-free micelle. The apparent lower calcium, magnesium, and phosphate contents, and absence of citrate in primary micelle were attributed to the removal of an adsorption layer from whole micelle. The qualitative and quantitative distribution of minerals in milk micelle is discussed and it appears that three zones could be distinguished: adsorbed double layer of ions, bound minerals, and casein counter-ions.