The linear axial compressibilities of a deuterated sample of TTF-TCNQ (tetrathiafulvalene-tetracyanoquinodimethane) have been measured by a neutron diffraction technique under hydrostatic pressures up to ∼ 20 kbar at room temperature. The observed compressibilities along the crystallographic axes are, respectively, ka = 2.7, kb = 4.7 and kc = 3.2 x 10-12 cm2/dyne. These results indicate a strong Coulomb type interchain interaction. It is suggested that the dominant part of the crystal cohesion results from a stacking of strongly dynamically polarized TTF and TCNQ molecules acting as effective molecular dipoles