[4] Ritvo held positions as a teaching fellow in psychiatry at Harvard Medical School, Tufts Medical School, and a fellowship in child psychiatry at James Jackson Putnam Children’s Center in Boston.

He self-published his experiences there in Drafted and Shafted: Memoirs of an Army Psychiatrist.

[6] Following a fellowship in child psychiatry at Reiss-Davis Clinic for Child Psychiatry, in Los Angeles from 1961–1962, he joined the faculty of the UCLA School of Medicine in 1962, where he served until he retired as professor emeritus.

[5] He was one of the psychiatrists who wrote the original definition of autism for the Diagnostic and Statistical Manual of Mental Disorders.

"[8] He and colleagues at UCLA identified a subclinical form of autism in the parents of autistic children.