evising a protocol for localization in a wireless sensor network is a formidable task. In this paper, we present a localization protocol for a wireless sensor network. In our protocol, a sensor computes its location using the locations of either anchors or sensors whose locations are already computed, and their distance estimates. Our protocol is distributed and does not need the availability of the topological information of the whole network at a centralized sensor before starting the computation. Our protocol is asynchronous as it does not need the clocks of sensors to be synchronized. Each sensor relies on its local clock. Our protocol is scalable and can be applied to a network irrespective of its size. We evaluate the performance of the proposed protocol by carrying out simulations. We study the effect of the number of anchors and the transmission range of sensors on the localizability and the error of localization. Further, we provide an expression for computing the probability that a sensor is localized in a sensor network.