In this paper we describe a recently proposed formalism for computing quantum response properties with quantum Monte Carlo (QMC) techniques. It is explained how this general formalism may be used to compute dynamic multipole polarizabilities as well as perturbational components of intermolecular interaction energies. Illustrative calculations for the dynamic dipole polarizability of the helium atom and for the perturbational components of the interaction energy of He2are presented. The practical limitations of this new scheme are discussed.