1. Selective sterilization as a prophylactic measure for the prevention of mental defect has been employed in varying degree in various states.2. Though the ratio of total sterilization to the estimated population is not a wholly satisfactory basis for comparison of the completeness of this program, it is the best available.3. Delaware has made the most extensive use of selective sterilization with 238 tubectomies per 100,000 inhabitants, followed by California, Virginia, Kansas and Oregon.4. In the years 1939 to 1943 inclusive, Virginia has been the most active, with 10.4 sterilizations per 100,000 per year, followed by California, Kansas, Delaware and North Dakota.5. In 1943 the most active program was in Utah, with 12.1 tubectomies per 100,000 of population, with Virginia, North Dakota, Delaware, Nebraska and California following.6. An important bar to a more extensive use of this form of prophylaxis is the public's lack of understanding of the differences between castration and sterilization.Abstract Teaser