This document describes major characteristics of 11,638 psychologists in the 1966 National Science Foundation's Register of Scientific and Technical Personnel who identified their positions as being related to the field of mental health. They make up 61.2 percent of all psychologists in the Register. Findings include: (1) The median age is 41, (2) The median years of professional experience is 12, (3) Two-thirds hold the doctoral, one-third the master's degree, and (4) Three-quarters are men, 96 percent of whom work full time compared with 79 percent of the women. Most important clinically-oriented work activities included clinical practice, 26 percent; test development, administration, and interpretation, 11 percent; and counseling practice, 8 percent. Other most important work activities were teaching, 20 percent; management, 17 percent; and research, 11 percent. Just over one-half work for educational institutions and one-quarter for government. Median salary is $11,000: $11,500 for men, $10,000 for women. Federal funds support the work of 5,142, including 916 Federal employees. (Author)