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We present HCN J=1--0 (88.6 GHz) images of the Orion Bar taken with the Berkeley--Illinois--Maryland millimeter array (BIMA). The HCN emission arises in the photodissociation region (PDR) of the Orion Bar. The HCN observations reveal information about the nitrogen chemistry in PDRs. We compare this HCN image with images of $^{12}$CO, $^{13}$CO, HCO+, H$_2$ 1--0 S(1) and 3.3$\mu$m dust feature all of which are tracers of warm gas and dust in the PDR.