Two proteins, lysozyme and ovalbumin, were adsorbed to smectite homoionic to first five elements of the alkali and the alkali earth series, hydrogen, aluminum, and lanthanum. Lysozyme was also adsorbed to Na-smectite in the presence of 10−3to 2.0 N NaCl solutions. Lysozyme adsorption by all clays was of the high affinity type, with 93 percent of the variance in the adsorption maximum being accounted for by the equation Amax= 290.2–5.5 (valence) - 96.8 (ionic radius) - 114.3 (Pauling electronegativity) - 6.5 (ionization potential). Adsorption of lysozyme by Na-smectite was decreased when the reaction occurred in solution with NaCl concentrations of 0.5 N or above. Adsorption of ovalbumin by the smectites was of the constant partition type and pH dependent. All homoionic clays except those saturated with H and Be adsorbed similar amounts of ovalbumin. Attempts to desorb the two proteins were generally unsuccessful, indicating that stabile complexes had been formed.