In the first study, 20 male and 20 female volunteers were studied under threat-of-shock and no-threat conditions with respect to anxiety levels, skin conductance, EEG auditory evoked response, and alpha-blocking variables. The threat-of-shock increased anxiety levels, skin conductance level, and fluctuations. The P300 component of the AER was greater in anxious individuals and habituation of the alpha-blocking response was retarded. In the second study, 12 anxious patients were compared with 12 normal subjects under threat-of-shock and 12 normal subjects under no-threat. Anxiety was associated with increased skin conductance fluctuations, larger P300 AER components, and impaired habituation of the alpha response.