Dr. Leventhal was one of only six women in the Harvard Medical School class of 1960. After graduating, she trained in pediatrics at the Massachusetts General Hospital and the Boston City Hospital, and in hematology at St Elizabeth's. In 1964, Dr. Leventhal moved to Maryland and worked at the National Cancer Institute of the National Institutes of Health in Bethesda, conducting clinical and laboratory research on leukemia and other childhood cancers.

In 1976, Dr. Leventhal joined the faculty of the Johns Hopkins University School of Medicine in Baltimore as an Associate Professor and was later made a full Professor of Pediatrics and Oncology. She served as the Director of the Division of Pediatric Oncology of the Johns Hopkins Oncology Center and helped found new inpatient and outpatient clinics there.

Dr. Leventhal co-authored the text book Research Methods in Clinical Oncology as well as hundreds of articles in scientific books and journals. She received numerous honors including the Federal Women's Award (1974), the Outstanding Career Woman of the National Council of Women (1979), and the Professional Achievement Award of the UCLA Alumni Association (1982). She was very active in professional societies, serving as an elected official in, among others, the American Society of Clinical Oncology (ASCO) and the American Association of Cancer Research. In 1993, ASCO established the Brigid Leventhal Travel Award to assist a woman doctor to travel to society meetings. She was a Founding Member of the Pediatric Oncology Group and a Founding Member and President of the Women in Cancer Research. Dr. Leventhal also served as a member of the St. Jude's Children's Hospital Scientific Advisory Board and the Recombinant DNA Advisory Committee of the National Institutes of Health.

Dr. Leventhal was honored by Baltimore Mayor Kurt Schmoke with a proclamation designating July 29,1992 as Brigid G. Leventhal Day in Baltimore. The Brigid G. Leventhal Memorial Lectureship at the Johns Hopkins Oncology Center is a lasting tribute to her commitment to scholarship and medical research and education.
Dr. Leventhal devoted her career to saving the lives of terminally ill children and to research to find better methods to treat deadly childhood cancers. She was known as a nurturing doctor, with a compassionate bedside manner, as well as a sharp intellect demanding rigorous standards for academic research. She was a supportive mentor to younger doctors and nurses and a wonderful friend to many classmates, colleagues and patients' families.

Dr. Leventhal's life was cut short by cancer, and she died on February 6,1994. She is missed most of all by the family she loved, including her husband of 32 years, Dr. Carl M. Leventhal, and their four grown children.