Solid-phase complexing of ibuprofen (IP) roll-mixed with beta-cyclodextrin (beta-CD) has been investigated by measurement of powder X-ray diffraction patterns and complex yields in powder mixture systems. The roll-mixed system of IP and beta-CD transformed readily to an amorphous form at the shear rate between rollers of 2.1 X 10(3) (s-1), to give an X-ray scattering pattern with three halo peaks around 13-degrees, 18-degrees and 24-degrees (in 2theta). An inner halo peak site of complex formation appeared to shift slightly toward a lower diffraction angle. The yield of IP complex increased with increasing roll-mixing periods and shearing rates, and reached more than 90% for 10 min at 2.1 x 10(3) (S-1) Shearing rate. The facts indicate that mechanochemical complexing of beta-CD should occur in molecules such as IP capable of forming inclusion complexes.