The scalable extension of H.264/MPEG4-AVC is a current standardization project of the Joint Video Team (JVT) of the ITU-T Video Coding Experts Group (VCEG) and the ISO/IEC Moving Picture Experts Group (MPEG). This paper gives an overview of the design of the scalable H.264/MPEG4-AVC extension and describes the basic concepts for supporting temporal, spatial, and SNR scalability. The efficiency of the described concepts for providing spatial and SNR scalability is analyzed by means of simulation results and compared to H.264/MPEG4-AVC compliant single layer coding.