Itano decided to complete a Ph.D. in chemistry because he wanted to pursue medical research in the laboratory rather than practice medicine clinically. Prior to his arrival at Caltech, Itano applied for and received a three-year American Chemical Society Predoctoral Fellowship in Chemistry, which supported him at Caltech. Itano stayed in Pasadena until 1954 at which time he relocated to the National Cancer Institute in Bethesda, Maryland. During his first four years at Caltech, Itano focused on sickle cell hemoglobin. During his last four years, he continued his research on sickle cell anemia and began looking for and learning about other abnormal hemoglobins. By 1954 Itano found, either by himself or in collaboration with others, three more abnormal hemoglobins. These abnormal hemoglobins that Itano discovered are considered the first four.

The work that Itano accomplished while at Caltech was impressive. In 1955 Pauling nominated Itano for an award given by the American Association for the Advancement of Science by citing Itano's sickle cell anemia and abnormal hemoglobin research. Additionally, Pauling acknowledged Itano's original contributions to hematology by stating that Itano instigated further research on abnormal hemoglobin and their hemoglobinopathies, of which about twelve had been discovered by this time. Itano did not receive this award; however, his contributions were immediately recognized in other ways. He had received the 1954 Eli Lilly and Company Award in Biological Chemistry and he was invited to give the George Minot lecture in 1955.

Pauling and Itano corresponded throughout the years after Itano left Caltech. They discussed the status of hemoglobin research and exchanged Christmas cards. Itano spent from 1954 to 1970 working in various positions for the National Institutes of Health, particularly as a surgeon for the National Cancer Institute and as a senior surgeon and medical director for the National Institute of Arthritis and Metabolic Disorders. In 1970 Itano went to the University of California at San Diego, where he retired in 1988 and became an emeritus professor of the Department of Pathology.