The mechanical behavior of boron pnictides has been analyzed by calculating the elastic properties by performing finite distortions of the lattice. The calculated sets of elastic constants C ij (i and j correspond to directions) for zinc-blende and qtz phases are given in Table . All C ij values are positive, indicating mechanically stable phases. qtz pnictides have systematically larger C 11 , C 33 and C 66 values than corresponding zinc-blende polymorphs due to the smaller volumes per formula unit. Along the BAs -BSb -BBi series, there is a tendency for the C ij values of zinc-blende and qtz phases to decrease due to the increase in atomic radii: r(As) = 1.2 Å, r(Sb) = 1.4 Å, r(Bi) = 1.5 Å, and consequently to increase in cell volume and compressibility.