Behavioral experiments were carried out on restrained, but otherwise fully active, squid to test the chemoreceptive capabilities of the olfactory organ. Specific chemical substances stimulated high-pressure jet escape responses when ejected from a small pipette into the area immediately around the olfactory organ. These included squid ink and L-Dopa (3,4 dihydroxyphenylalanine) as well as agents that block voltage-dependent potassium channels, such as quaternary ammonium ions and 4-aminopyridine. Experiments designed to map chemosensitivity spatially identified the olfactory organ as the receptive site. Unilateral application of a topical local anesthetic to an olfactory organ selectively and reversibly abolished responsiveness on the treated side only. The olfactory organ can thus mediate detection of water-borne chemicals. This detection, in turn, is linked to motor control pathways involved in initiating escape-jetting behavior.