The partition ratioDof Al(III) between aqueous chloride/bisulfate solutions of constant ionic strength (5.0) and methyl ethylketone (MEK) or methyl isobutyl ketone (MIBK) was investigated radiometrically as a function of the chloride/bisulfate ratio and aqueous acidity. With MIBK, the plot ofDvs chloride/bisulfate showed a maximum. Results may be explained by assuming the extraction of the following species: KtH+·AlCl4-, KtH+-AlCl2(HSO4)2- and KtH+·Al(HSO4)4, where KtH+represents a solvated hydrogen ion. Formation constants for these complexes were calculated.