Most of the matter in the Universe appears to be not only dark but also non-baryonic. After reviewing the observational evidence for dark matter and some of the more popular particle dark matter candidates I'll focus on WIMP (weakly interacting massive particle) direct detection. Current experiments are just reaching the sensitivity required to detect WIMPs and the DAMA collaboration indeed claim to have detected a WIMP signal. I'll show that the expected WIMP signals depend sensitively on astrophysical input, in particular the dark matter distribution on sub-mpc scales.