Abstract : Multistatic radars utilize multiple transmitter and receiver sites to provide several different monostatic and bistatic channels of observation. Multistatic passive and active radar systems can offer many advantages in terms of coverage and accuracy in the estimation of target signal parameters. Unfortunately, their performances are heavily sensitive to the position of receivers and transmitters with respect to the position of the target. It is well know that geometry factors play an important role in the shape of the ambiguity function (AF) which is often used to measure the possible global resolution and large error properties of the target parameters estimates. In this work we exploit the relation between the ambiguity function and the Cramer-Rao lower bound (CRLB) to calculate the bistatic CRLBs of target range and velocity and so obtaining a local measure of the estimation a ccuracy of these parameters. We also propose an algorithm for choosing in a multistatic scenario, along the trajectory of the tracked target, the pair transmitter-receiver with the best asymptotic performance calculated in terms of CRLB on estimation accuracy.