In shared memory packet switches, buffer management schemes can improve overall loss performance, as well as fairness, by regulating the sharing of memory among the different output port queues. Of the conventional schemes, Static Threshold is simple but does not adapt to changing traffic conditions, while Pushout is highly adaptive but difficult to implement. We propose a novel scheme called Dynamic Threshold that combines the simplicity of Static Threshold and the adaptivity of Pushout. The key idea is that the maximum permissible length, for any individual queue at any instant of time, is proportional to the unused buffering in the switch. A queue whose length equals or exceeds the current threshold value may accept no more arrivals. An analysis of the Dynamic Threshold algorithm shows that a small amount of buffer space is (intentionally) left unallocated, and that the remaining buffer space becomes equally distributed among the active output queues. We use computer simulation to compare the loss performance of Dynamic Threshold, Static Threshold, and Pushout. Dynamic Threshold control is shown to be more robust to uncertainties and changes in traffic conditions than Static Threshold control. This paper appears in IEEE/ACM Transactions on Networking , Vol. 6, No. 2, April 1998, pp. 130-140. 1