A behavior therapist is a certified and trained professional who is required to have highly technical knowledge in devising/implementing a behavioral program for each individual. The purpose of this study was to offer practical information attesting the importance of behavior therapists in our society and immediate needs of professional training programs for them. It also was to elucidate the functional aspects of behavior therapist, which facilitates more practical scheme of systematic behavior therapist training programs. The data of this study manifested pressing needs of behavior therapies for individuals with disabilities whose population reaches 3.09% out of the entire population in Korea. About 7,700 behavior therapies are needed for 78,625 individuals with disabilities staying in residential rehabilitation institutes. Also, about 1,200 behavior therapies are urgently needed for 24,380 children with disabilities in 134 special education schools. To meet the immediate needs for individuals with disabilities, we need about 9,000 behavior therapists at present. Additionally, 18,468 schools, through kindergartens to high schools, in Korea demands about 36,936 behavior therapists, 2 behavior therapists per each school. Accordingly, we need around 45,936 behavior therapists at a rough estimate in 2001. The study analyzed the function, immediate needs, and importance of behavior therapists and suggests that it is pressing to establish an authorized credential system for behavior therapists.