This paper addresses the problem of optimal packetization for a fine granularity scalable (FGS) bitstream. A very general performance metric for streaming FGS bitstreams over packet erasure networks is first defined and analyzed. Then three packetization strategies, namely baseline packetization, binary-tree packetization and optimal packetization are presented, justified and compared. Finally, some experimental results are presented to demonstrate the effectiveness of the packetization schemes.