Dr. Klein graduated from M.I.T. with his B.S. degree and subsequently from the Johns Hopkins School of Medicine. At M.I.T. he was a Phi Beta Kappa scholar, as well as President of the Chemistry Honorary Society. At Johns Hopkins he was elected to the AOA medical honorary society. After completing two years of residency training at Strong Memorial Hospital, Dr. Klein returned to Johns Hopkins as one of its first two Henry J. Kaiser Foundation Fellows in Internal Medicine. Following fellowship, Dr. Klein was invited to join the full-time medical faculty at Johns Hopkins. In that capacity he did a mixture of clinical work, teaching, research and administration publishing 39 papers and abstracts and serving as Director of the General Medicine Fellowship Training Program and Director of the Senior Student Longitudinal Ambulatory Clinic.

After spending 4 years on the full-time faculty at Johns Hopkins, Dr. Klein moved to Washington to begin practicing medicine full-time at Foxhall Internists. Dr. Klein continues to hold a part-time faculty appointment at Johns Hopkins, as well as at the Georgetown University School of Medicine. Since arriving in the Washington area, Dr. Klein has been active in several medical organizations. He is a past president of the D.C. Society of Internal Medicine and is currently governor of the D.C. chapter of the American College of Physicians.

Dr. Klein was awarded the John H. Maher Laureate Award from the American College of Physicians for service to his patients and fellow physicians. He has been selected multiple times as a "Top Doctor" in surveys published in The Washingtonian Magazine, Washington Consumers' Checkbook, Best Doctors in Southeastern United States, Guide from the Center for the Study of Services, and Town and Country Magazine. He is board certified in Internal Medicine, as well as has board recognition in the area of Geriatrics.

Dr. Klein has been married for 24 years to Gayle Better Klein and has two children (Marni age 14 and David age 8) who help keep him young.