Vocal indicators of stress are determined by frequency, frequency variability, intensity, and timing. For example, anger and fear appear to be accompanied by raised frequency, and grief, contempt and indifference by lowered speaking fundamental frequency (SFF). To be helpful to law enforcement agencies, data based on this metric must be compared with baseline curves for the same individual, obtained from speech produced in a neutral speaking environment. When talking, stressed individuals exhibit behaviors such as voicing irregularities, discontinuties in frequency contours, irregular vocal fold vibration, and even vocal tremor. Examination of the vocal indicators of psychosis are important in providing data concerning the speech characteristics of individuals experiencing short-term stress of a nonclinical type. Speech of schizophrenics exhibit strain; harshness; register changes (to falsetto); volume changes (to loud); dysarticulation; speed changes with inappropriate alternations; 'gloomy, dull timbre;' and monotonous melody. Moreover, voicing irregularities of schizophrenics are also found in the speech of individuals experiencing high levels of stress. A review of the vocal correlates of affective disorders (i.e., general, involutional, or manic-depression), suggests that such patients probably use different speaking patterns than do normals. While there may be no classical pattern of the speech/voice characteristics of depression, these patients probably exhibit reduced speaking intensity; reduced pitch range; slower speech; reduced intonation; and a lack of linguistic stress. Due to conflicting data, though, caution is necessary when attempting to generalize the speech/voice characteristics of psychotics. Initial findings indicate that voice analyzers, such as the Psychological Stress Evaluator or the Voice Stress Analyzer, are not very effective in detecting low risk lies; for high risk lies, the correct identifications appear to range from chance or a little above to very high scores. Some studies indicate that these devices constitute not nearly as powerful a tool as does the polygraph, the limitations of which are well known. Moreover, no one as yet has tested any of the voice analyzers with speech samples that have been transmitted over a telephone, and research of this type is very much needed. A valid tool for law enforcement agencies to use in detecting deception and duplicity does not presently exist. Tabular data and 85 references are provided.