She graduated in psychology from UCLA in 1955 and began to study medicine there before transferring to Harvard Medical School.
[1] After completing medical school, Leventhal was an intern and pediatric resident at Massachusetts General Hospital.
She served as a resident at Boston City Hospital for one year and completed a one-year fellowship in hematology at St. Elizabeth's Medical Center.
At the NCI, she sat on the Recombinant DNA Advisory Committee and a subcommittee on human gene therapy; she headed the Chemoimmunotherapy Section from 1973 to 1976.
While developing new treatments for childhood cancers, she established the inpatient unit and outpatient clinics for pediatric oncology patients.