Abstract
The existence of dark matter was suggested, using simple gravitational arguments, seventy years ago. Although we are now convinced that most of the mass in the Universe is indeed some nonluminous matter, we still do not know its composition. The problem of the dark matter in the Universe is reviewed here. Particle candidates for dark matter are discussed with particular emphasis on Weakly Interacting Massive Particles (WIMP's). Experiments searching for these relic particles, carried out by many groups around the world, are also reviewed, paying special attention to their direct detection by observing the elastic scattering on target nuclei through nuclear recoils. Finally, we concentrate on the theoretical models predicting WIMP's, and in particular on supersymmetric extensions of the standard model, where the leading candidate for WIMP, the neutralino, is present. There, we compute the cross-section for the direct detection of neutralinos, and compare it with the sensitivity of detectors. We mainly discuss supergravity, superstring and M theory scenarios.