In 18 normal volunteers, lorazepam (2.5 mg) compared with placebo significantly impaired performance in a verbal learning task, in the digit-symbol substitution test, and in symbol copying and number cancellation tasks. These impairments were found equally in subjects with high and low state anxiety and in subjects with high and low trait anxiety. Caffeine citrate (125 to 500 mg) significantly improved performance on the digit-symbol substitution test when given alone and reduced the lorazepam impairment. In the symbol copying test caffeine counteracted the lorazepam impairment. Lorazepam produced a significant loss of appetite and made the subjects feel significantly more dizzy, physically and mentally tired, withdrawn and tranquil, and significantly less anxious. Caffeine citrate (500 mg) counteracted the lorazepam effect of reducing anxiety and making the subjects feel more relaxed.