Colloids are potentially important adsorbents in natural environments and their characterization is a necessary step in understanding their chemistry and geochemistry. A method for determining the relative molecular weight distribution of alumina, silica, and hydroxyaluminosilicate colloids by high performance gel filtration chromatography utilizing a G3000 PWXL column and a refractive index detector is reported. Analytical parameters that affect the molecular weight distribution of the inorganic colloids are discussed. The optimum analytical conditions for performing this analysis were found to be an ionic strength of 0.1M(as NaNO3), a pH of 5, a flow rate of 0.8 mL/min, and a colloid concentration of 400 mg/L.