Hybrid Distributed Coordination Function(HDCF),a modified medium access control protocol of IEEE 802.11 standard,is proposed in this paper to support both smart adaptive array antennas and normal omni-directional antennas simultaneously in one wireless LAN.Omni-directional antennaus follow the standard Distributed Coordination Function(DCF)and smart antennas follow the Directional DCF (DDCF).The proposed DDCF is based on Hybrid Virtual Carrier Sense(HVCS)mechanism.which includes Omni-directional Request-To-Send/Clear-To-Send(ORTS/OCTS)handshake mechanism and directional data transmission.HDCF is compatible with DCF.When a node transmits in a directional beam,the other nodes can multiplex the physical channel.Hence,HDCF supports Space Division Multiple Access(SDMA).Simulation results show that HDCF can support hybrid antennas effectively and provide much higher network throughput and lower delay and jitter than DCF does.