The effects of oxazepam and a standardized extract of kava-roots (WS1490, W. Schwabe, Karlsruhe) on reaction time and event-related potentials (ERPs) were investigated in a visual search paradigm using a double-blind design in young, healthy males. Significant effects of oxazepam were obtained in a number of psychometric tests as well as search time and quality. Several ERP components of different latency, topography and functional significance were affected by the medications. Oxazepam led to a reduction of the amplitude of the parietal N1, frontal N2, posterior contralateral N2, and occipital P3 components. WS 1490 was associated with a greater posterior N1, posterior contralateral N2, and occipital P3. The effects are discussed in the light of the functional properties of the components and provide clues as to the psychological site of action of the drugs.