Monte Carlo (MC) calculations on various models are reviewed : Ising models with random nearest neighbour as well as random infinite range exchange, Heisenberg models with random nearest neighbour as well as RKKY exchange. Susceptibilities, specific heats and internal field distributions are compared to relevant experiments and theories. Zero-temperature properties are described in the context of concepts on the nature of spin ordering in spin glasses. Time-dependent properties are presented for nearest neighbour Ising spin glasses. The anomalous slow relaxation in the "frozen" state is traced back to the high degeneracy of the ground state, and implications for the existence of phase transitions are discussed