Coal cleaning by selective agglomeration of an aqueous suspension of coal particles was demonstrated on a laboratory scale by employing a colloidal dispersion of microscopic gas bubbles as an agglomerant. The microbubbles were produced by saturating water with gas under pressure and then releasing the pressure as the water was agitated. The formation and stabilization of microbubbles was facilitated by employing a small amount of i-octane. Agglomeration was carried out in a closed system using a high shear rate and with no additional air present. The resulting agglomerates Boated readily since they consisted of a mixture of coal particles and microbubbles. Therefore, the agglomerates were recovered by allowing the treated material to separate into distinct layers under quiescent conditions. The upper product layer held most of the coal with greatly diminished ash content while the bottom layer was composed largely of ash-forming mineral matter. The effects of various process parameters were studied including solids concentration, i-octane concentration, and air saturation pressure. In addition, the results achieved with two agglomeration stages were compared with the results of a single stage.