The effects of adrenaline, noradrenaline, isoproterenol, Alupent, histamine, acetylcholine and serotonin on the isolated rabbit spleen were studied in vitro. The myographic method of recording was used. It was found that all these substances with the exception of Alupent evoked contraction of the rabbit spleen. The contractile response of the spleen was greatest after adrenaline, insignificantly smaller after noradrenaline, very small after isoproterenol and absent after Alupent. A still smaller response was observed after histamine, acetylcholine and serotonin.