1. A study of 708 Selective Service Law violators admitted to the Medical Center for Federal Prisoners during World War II is presented.2. The subjects naturally group themselves in three categories, namely, technical violators, Jehovah's Witnesses, and conscientious objectors.3. Technical violators comprise the largest group. They differ very little from the run-of-the-mill prisoners. Only 25% of the technical violators would have been suitable for military service if they had submitted to induction.4. Jehovah's Witnesses were the next largest group. They refused military service on the grounds that it would interfere with their religious activities or demanded to be exempted from all service on the grounds that they were ministers. Jehovah's Witnesses represent a segment of the noncriminal population of the country. Unlike the technical violators 80% would have been fit for military duty if they had submitted to induction.5. The conscientious objectors were the least in numbers, but the most in nuisance value. Like the Jehovah's Witnesses the majority were not criminals in the ordinary sense of the word. They refused military or alternative service either because of religious or because of philosophical scruples against war. Only 37% would have been found fit for military duty if they had submitted to induction.6. Suggestions are made for improving future Selective Service procedures.