Following Hannah’s death in 1941, Stone succeeded his wife as Medical Director of the Margaret Sanger Research Bureau, and later ascended to the position of Director of the facility. Under Stone’s direction, he expanded the facility’s services to include marriage counseling and fertility and sterility services, including early artificial insemination procedures, and the institution became informally referred to as the clinical research arm of the Planned Parenthood Federation of America. He maintained a close working relationship with Sanger as director and collaborated with her on efforts to increase birth control awareness amongst the American public. Stone advised women of all backgrounds on feasible options for their reproductive health and collaborated with international colleagues to heighten initial awareness for the need for family planning resources in developing nations.

 Stone assisted Sanger in the founding of the International Planned Parenthood Federation in 1952, and served as the organization’s vice-president during the 1950s. He published articles on topics including family planning, marital relations, fertility, sterility, and sex education. Stone also published The Premarital Consultation, the first manual on marital relations written for physicians, with physician Lena Levine in 1956. He died in 1959.