The problem of state estimation for linear or nonlinear models with unknown parameters is very Lmportant in many engineering problems. As such it has been addressed extensively through the use of statistical methodologies i.e. ALF, EKF, etc. In this paper the solution to the problem of adaptive estimation for unknown state variable or chaotic models through the use of adaptive dynamic neural estimators is proposed. The proposed adaptive neural estimators are developed and their advantages are discussed. Extensive computer simulations of the application of the proposed adaptive neural estimator to state estimation as well as chaotic series prediction Illustrate the effectiveness of the adaptive neural solution.