Electrocorticograms of rats were recorded after administration of increasing doses of the major metabolite of nortriptyline (NT), E-10-hydroxynortriptyline (E-10-OH-NT). The results were compared with those of NT administration. In visual as well as computerized evaluations, E-10-OH-NT demonstrated clear antidepressant properties, thus confirming previous experiments in depressed patients. There is some evidence that E-10-OH-NT also has an anxiolytic profile. The results with the parent drug NT were not so pronounced. Since E-10-OH-NT has been shown to be devoid of side effects when previously administered to humans, this substance is clearly to be considered of interest for potential development into a new antidepressant. Whether or not the anxiolytic profile is of clinical interest needs to be investigated further.