—In this paper, we consider user selection criteria for various multiple input multiple output (MIMO) detectors to exploit the multiuser diversity. It is shown that the user selection criterion plays a crucial role in exploiting both multiuser and receive (or spatial) diversity. We also show that the maximum likelihood (ML) and even some low complexity suboptimal detectors (based on the lattice reduction (LR)) can achieve a full multiuser and receive diversity when the user selection criterion is properly chosen.