As an undergraduate, Dr. Diaz was co-founder of UC Davis CHE, a Latino Pre-medical club in 1972. He co-founded Clinica Tepati, a free clinic for Spanish-speaking patients in 1974 where he has volunteered as an undergraduate student, medical student, resident and attending physician. He graduated from the UCSF School of Medicine and is a board certified Family Practice and Occupational Medicine. He was a founding member of the National Hispanic Medical Association, the National Hispanic Health Foundation and the National Hispanic Pharmacists Association. He is currently the Chairman of the Board of Directors of the National Hispanic Health Foundation. He is a Volunteer Clinical Professor in the Department of Family and Community Medicine of the University of California, Davis and at CA Northstate University College of Medicine.