Abstract: Eighteen compounds with structures related to chlorpromazine, of which the ring was opened according to (Ⅰ), have been investigated. In mice, the sedative-tranquillizing actions of these open ring analogues of chlorpromazine disappeared, their anti-histamine action in guinea pig was significantly reduced, but the sulface anaesthetic potency on rabbit cornea was increased; among them NM-568 (β-piperidino, N-β'-(p-chlorophenylmercapto)-ethyl-propionanilide hydrochloride) is the strongest. In comparison with sovcaine and procaine the following anaesthetic ratios were obtained by the various methods used: (1) Anaesthesia test on rabbit cornea: the surface anaesthetic potency of NM-568 is approximately the same as sovcaine, and about 1060 times that of procaine. (2) Intracutaneous-wheal test in guinea pigs (Bülbring and Wajda's method):the potency of procaine,1; NM-568, 27.5; sovcaine, 22. (3) Sciatic nerve block test in mice: the potency of procaine, 1; NM-568, 16; sovcaine, 39. (4) Spinal anaesthesia in winter toad: the potency of procaine, 1; NM-568, 9; sovcaine, 8. In mice, the acute toxicity after intraperitoneal injection of NM-568 is about half of that of sovcaine, but 3 times greater than that of procaine; Its irritant action on the skin (Trypan blue test) and cornea in rabbits is stronger than that of sovcaine and procaine. Among these 18 analogues of chlorpromazine, NM-572 (N-γ-morpholino-propyl, N-β'-(p-chlorophenylmercapto)-ethyl-aniline dihydrochloride) and NM-578 (N-γ-piperi-dino-propyl, N-β'-(p-chlorophenylmercapto)-ethyl-aniline dihydrochloride) in large doses (about 1/5 M.L.D.) revealed an anti-electroshock effect for 2 hours.