For joint state-parameter estimation in linear time-varying (LTV) multiple-input-multiple-output (MIMO) systems, a new approach to the design of adaptive observers is proposed in this note. It is conceptually simple,and computationally efficient. Its global exponential convergence is established for noise-free systems. In the presence of noises, it is proved that the estimation errors are bounded and converge in the mean to zero if the noises are bounded and have zero means. Potential applications Eire fault detection and isolation, and adaptive control.