Like Dr. Amadeo Cruz, Dr. Gatmaitan rose from the ranks. He first joined the DOH in 1930 as a physician in the Negros Occidental Provincial Office. He became President of the Sanitary Division in Bulacan from 1932 – 1934. He was Medical Officer in the Bureau of Health, Chief of the Section of School Health Supervision, and then Undersecretary of Health for Medical Services in 1962. He became acting Secretary of Health in December 1971 and was appointed Secretary only in January 1973. He became the first Minister of Health in July 1978. With a total duration of 8 years, his administration was the longest uninterrupted term as Secretary of Health.

The POPIIBRD loan project started during his term. The main feature of POP I was the “Restructured Health Care Delivery System” which provided for the creation of Barangay Health Stations in the effort to provide one Midwife for every 5,000 population. The Midwives were also given delegated authority from the health center physician to perform expanded tasks and responsibilities in general care.

In 1976, the Rural Health Practice Program (RHPP), which fielded new medical and nursing graduates to the rural areas for 3-6 months, was implemented. Field implementation of the Medicare Act of 1969 occurred during his term. He tried to initiate the integration of preventive and curative care but his efforts met strong opposition from the hospital advocates. The Institute of Health Sciences in Tacloban, stepladder training of midwives, nurses and doctors, was initiated during his term in 1976. The Expanded Program on Immunization was formally launched in 1976.

His term also marked the construction of huge medical centers in Metro Manila: The Heart Center for Asia, the Lung Center of the Philippines, and the Philippine Children’s Medical Center, all of which were popularly referred to as somebody’s “Disease Palaces”.