Umespirone [KC 9172, KC 7218] is a serotonin 1A receptor agonist that was undergoing phase I clinical trials with Solvay in the Netherlands as a potential treatment for anxiety and psychotic disorders. Umespirone prevented the behavioural consequences of withdrawal from diazepam. Umespirone also had an anxiolytic profile of action in the tests of rat social interaction and in the marmoset exposed to a human threat. Umespirone reduced the hyperactivity induced by the infusion of dopamine into the nucleus accumbens of rat. In radioligand binding assays umespirone demonstrated nanomolar affinity for the alpha 1-adrenoceptor and the 5-HT1A and dopamine D2 receptors.