A recently developed technique for the acoustical analysis of speech is described. Speech is analysed electronically for the presence or absence of a microtremor having a frequency of about 10 Hz. This tremor is said to be attenuated in states of psychological stress. The paper presents data supporting the validity of this as a measure of anxiety, using states of both normal and pathological anxiety. An objective scoring system is proposed to overcome some of the problems of unreliability. A number of practical advantages of the voice technique are described.