In 1939, Gamble began flying Puerto Rican doctors to New York to learn the latest in sterilization techniques. Earlier in the decade he had staffed birth control clinics, established by Franklin D. Roosevelt’s Puerto Rican Relief Administration, with his own fieldworkers and used them as sites for recruiting candidates for sterilization. Many of the women who submitted to tubal ligation were not made to understand that it was permanent. Some Gamble-supported facilities reported refusing admittance to women with who had given birth two or more times if they did not ‘consent’ to la operación. In 1968, roughly 30 years into Gamble’s involvement in Puerto Rico, women there had the highest sterilization rates in the world.