In this paper, we consider a statistical multiplexer fed by heterogeneous ON and OFF sources. We provide closed-form results on the tail behavior of the queue-length distribution for statistical multiplexers, where the tail behavior can be expressed in terms of traffic parameters such as the first and second moments of ON and OFF periods for individual sources. Since our results are of simple closed-form, they can be used to provide a simple and efficient way to predict the tail behavior and the impact of traffic parameters on performance.