We present the next-to-leading order calculation of two four-jet event shape
variables, the D parameter and acoplanarity differential distributions. We find
large, more than 100% radiative corrections. The theoretical prediction for the
D parameter is compared to L3 data obtained at the Z peak and corrected to
hadron level.Comment: 11 pages, latex with aps, epsf, rotate styles 3 tables, 3 figures
typo in eq. 10 corrected, note and reference added, introduction revise