[1] Ley's research group focuses on the genetics and genomics of acute myeloid leukemia (AML).

His work is focused on identifying the mutations and epigenetic events that are responsible for the initiation and progression of AML.

[3][4] He has gone on to develop projects that will use whole genome sequencing to help diagnose and treat patients with AML.

[6] Dr. Ley's laboratory has also helped to define the roles of granzymes for the functions of cytotoxic and regulatory T cells.

He did his internship and residency in Medicine at Massachusetts General Hospital, was a clinical associate at the NHLBI (National Heart, Lung, and Blood Institute), a Hematology-Oncology Fellow at Washington University Medical Center, and a senior investigator at the NHLBI before moving to Washington University in 1986.