Video transmission on multiuser wireless channels faces great challenges due to diverse Quality of services (QoS) requirements, harsh wireless channels and scarce radio resources. Combining scalable video coding with OFDM technique provides an efficient solution to satisfy diverse requirements from heterogeneous mobile users. In this paper, we propose a cross-layer resource allocation scheme for scalable video transmission over multiuser OFDM systems. Different video quality layers, including the base layer and multiple enhancement layers, are allocated to different subcarriers. A suboptimal subcarrier, bits and power allocation algorithm is applied to minimize the total transmit power. Simulation results show the proposed scheme obtains similar video quality to that of single-layer coding scheme, but with less transmit power.