Abstract 1. 1. Summated neural responses to various chemical stimuli were recorded from the peripheral nerve innervating the lateral line organs which occur on the upper snout of the giurine goby, Gobius giurinus. 2. 2. The threshold for monovalent chloride salts was estimated to be at around 10 −3 M, while that for divalent chloride salts, at around 10 −4M. The order of the stimulatory effectiveness was RbCl ⩾ NH 4Cl ⩾ KCl ⩾ NaCl ⩾ LiCl ⩾ CsCl for monovalent salts and BaCl 2 > CaCl 2 ⩾ MgCl 2 SrCl 2 for divalent salts. 3. 3. Of 17 amino acids only two acidic amino acids, l-Glu and l-Asp, were stimulative and the sensitivity of the lateral line organs to them was considered to be due to the hydrogen ion, since response magnitudes to the amino acids depended upon solution pH and were similar to the response magnitude to HCl of the same pH. 4. 4. Many typical free neuromasts were found to form the so called pit-line on the upper snout region, but where no canal organs were observed.