Based on molecular dynamics simulations, the mechanical properties and buckling behavior of boron-nitride nanotubes under the action of torsional load are investigated. According to the results, the torsional properties of a boron-nitride nanotube are higher than those of its carbon counterpart. The effect of geometrical parameters on these parameters is also investigated. It is observed that by increasing the radius of nanotubes of the same length, unlike the critical shear strain, the critical torque considerably increases. The effect of chirality is also found to be negligible in the cases of critical shear strain and buckling mode, unlike the critical torque. (C) 2014 Elsevier B.V. All rights reserved.