Adaptive CSMA algorithms have attracted considerable attention, due to their throughput optimality, utility maximizing properties, and amenability to simple distributed implementation. In this paper, we investigate the impact of heavy-tailed traffic on the performance of a queue length based adaptive CSMA algorithm. Specifically, we consider two conflicting links that share a channel using adaptive CSMA. One of the links serves heavy-tailed traffic, while the other link serves light-tailed traffic. Our main contribution is in demonstrating a threshold phenomenon in the relationship between the arrival rates and the queue backlog distributions. In particular, we show that when the arrival rate of the light-tailed traffic is less than a threshold value, the light-tailed traffic experiences a light-tailed queue backlog at steady state, whereas for arrival rates above the same threshold, the light-tailed traffic experiences a heavy-tailed queue backlog. Comparing this result to a corresponding result for max-weight scheduling [8], we conclude that adaptive CSMA is potentially more robust to bursty traffic, compared to max-weight scheduling. © 2012 IEEE.