SPEAKER RECOGNITION BY LISTENING, VISUAL RECOGNITION OF SPEAKERS BY SPECTROGRAPHIC COMPARISON, AND SPEAKER RECOGNITION BY MACHINE, ARE EXPLAINED. METHODS OF EXPERIMENTATION, INTRASPEAKER VARIABILITY, ON THE MICHIGAN STATE UNIVERSITY VOICE IDENTIFICATION PROJECT, IS PRESENTED. RESULTS OF 673 VOICES EXAMINED BY STUDY OF 42,432 SPECTROGRAMS ARE GIVEN WITH CONCLUSIONS, INDICATING DEFINITE VALUE OF VOICE IDENTIFICATION IN LAW ENFORCEMENT. SPECIAL TRAINING REQUIREMENTS OF IDENTIFICATION TECHNICIANS IS DISCUSSED. APPENDIXES CONTAIN STATISTICAL ANALYSIS OF THE PROJECT AND PRACTICAL APPLICATIONS OF VOICE IDENTIFICATION IN CRIMINAL INVESTIGATION. LISTS OF REFERENCES ARE FOUND THROUGHOUT THE REPORT.