The thickness ranges and conditions to form the supersaturated solid solution in Al-Cr alloys were investigated with various rapid solidification conditions. Al-Cr alloys, rapidly solidified by using the small droplet chill quenching method, were examined by means of micro-vickers hardness, lattice parameter, thermal analysis and microscopic observation. The results obtained were as follows; 1. With the increase of solidification rate, the solidified structures were changed to intermetallic compound ＋ solid solution, incompletely supersaturated solid solution, completely supersaturated solid solution, in turn. 2. The minimum solidification rate required to form completely supersaturated solid solution was 2.5×10＾(－2)㎝/sec, 3.6×10＾(-2)㎝/sec and 6.0×10＾(-2)㎝/sec for Al-1.0wt%Cr, Al-1,2wt%Cr and Al-1.5wt%Cr, respectively. 3. The maximum distance from the chill surface required to form completely supersaturated solid solution was 5㎜, 1.3㎜ and 0.3㎜ for Al-1.0wt%Cr, Al-1.2wt%Cr and Al-1.5wt% Cr, respectively.