The effect of three-body interatomic contributions in the equation of state of He-4 are investigated. A recent two-body potential together with the Cohen and Murrell [Chem. Phys. Lett. 260, 371 (1996)] three-body potential are applied to describe bulk helium. The triple-dipole dispersion and exchange energies are evaluated subjected only to statistical uncertainties. An extension of the diffusion Monte Carlo method is applied in order to compute very small energies differences. The results show how the three-body contributions affect the ground-state energy, the equilibrium, melting and freezing densities. (C) 2003 American Institute of Physics.