A　novel　adaptive　observer-based　control　scheme　is　presented　for　synchronization　and　suppression　of　a　class　of　uncertain　chaotic　system.　First,　an　adaptive　observer　based　on　an　orthogonal　neural　network　is　designed.　Subsequently,　the　sliding　mode　controllers　via　the　proposed　adaptive　observer　are　proposed　for　synchronization　and　suppression　of　the　uncertain　chaotic　systems.　Theoretical　analysis　and　numerical　simulation　show　the　effectiveness　of　the　proposed　scheme.