It is worth noting that the neuronal states in large-scale NNs are usually not fully measurable. Thus, in many practice applications, estimating the states of neurons through available measurements is important. The chapter addresses the problem of state estimation for discrete-time NNs with multiple time-varying transmission delays. The involved NNs include discrete-time HONNs and BAMNNs. A direct method based on system solutions is proposed to establish the desired state observers for discrete-time HONNs and BAMNNs with multiple time-varying transmission delays, respectively.