<p> Until now, the nuclear many body problem has been restricted almost entirely to considerations of the two-body force. However the meson theory of nuclear forces predicts that the exchange of mesons between three or more particles will give rise to a three-body or may-body force. The meson theory which has succesfully explained the main features of the phenomenological nucleon-nucleon potential, is expected to provide a good basis for the study of three-body nuclear forces. Three-body nuclcear forces can occur among baryons such as N, ∧, Σ, and Ξ. So far, however only bound states of nucleons(nuclei) and of nucleons and ∧ (hypernuclei) have been observed experimentally. Hence only the three-nucleon force and the ∧NN force are considered. It will be seen that the ∧NN force plays a more important role than the three-nucleon force. Thus in the present work the ANN force will be studied in greater detail than the three-nucleon force. First the long and intermediate range parts of the ∧NN force are derived from meson theory. Their effects on the binding energies of ^H,^5He and nuclear matter are then estimated. Since the short range part of the force is not known, no definite conclusion can be drawn. However it is found that the three-body ∧NN force can play and important role in the nuclear structure problem. The effects of the three-nucleon force in ^3H and in nuclear matter are also briefly discussed. </p> / Thesis / Doctor of Philosophy (PhD)