Rats that are placed in a novel environment containing a probe will explore the environment and the probe. Exploration of the probe is reduced when the probe is electrified. We here report that chlordiazepoxide blocks this inhibition, and have determined some of the pharmacological features of this new experimental procedure. The procedure appears to be sensitive to the effects of several benzodiazepines, barbiturates, and related compounds. Limited activity was observed with most 5-HT antagonists, ritanserin, an anticholinergic, a β-adrenergic blocker and a neuroleptic. Of the antidepressants, only imipramine had some limited activity. Inactive compounds in this procedure include benzodiazepine antagonists, buspirone, convulsants, opiates, an opiate antagonist, stimulants, a putative DA agonist and antagonist, histamine antagonists, a cholinomimetic, anticholinergics, a NE antagonist, α2 agonists, an α2 antagonist, MAO inhibitors, 5-HTP and LSD.