This paper proposes a new concept of multiple-input multiple-output (MIMO) detection, aiming at minimizing the average computational cost. The detection methods, according to the estimated channel state information, are adapted to deliver just acceptable error rate. Performance of two popular MIMO detectors is analyzed. Based on these analyses, a channel adaptive MIMO (CA-MIMO) receiver with a novel method-selection strategy is investigated. Simulation results demonstrate that the proposed CA-MIMO detector, operating at as low SNR as the sphere search does, achieves huge average complexity saving.