AGA-MAC: Adaptive Geographic Anycast MAC Protocol for Wireless Sensor Networks This paper presents AGA-MAC: an adaptive geographic any cast medium access control (MAC)protocol for wireless sensor networks (WSNs). The protocol aims at reducing the sleep-delay problem of asynchronous preamble-based MAC protocols by selecting opportunistically the next relay node from a set of candidates. The size of the Forwarding Candidate Set (FCS) is influenced by a threshold parameter in our protocol. In order to outperform other existing any cast asynchronous protocols, we analyze the effect of different network densities, and threshold values in the network latency. The analysis is both mathematical and experimental using simulations. Results of our simulations showed that, for selected thresholds, our protocol outperformed by approximately 17% both the GeRaF and the well known X-MAC protocol for intermediate data packet size. For other sizes, our protocol followed the results of the best performing alternative, which could be GeRaF or X-MAC.