Duncan A.D. Mackay, 92, a former Foreign Service officer who retired from the Inter-American Development Bank as a member of its secretariat, died Jan. 15 at the Ingleside at Rock Creek retirement community in Washington. He had congestive heart failure.

A son, D. Keith Mackay, confirmed the death.

Mr. Mackay worked in the Foreign Service from 1947 to 1968, mostly as a political officer. His assignments included Saigon, Panama City, Lisbon and Mexico City.

He then joined the Inter-American Development Bank and was predominately a member of the secretariat until his retirement in 1985.

Duncan Alexander Duff Mackay was born in Lima, Peru, where his parents were missionaries for the Church of Scotland. His father, John, became president of the Princeton Theological Seminary in New Jersey.

The younger Mackay completed high school in Hightstown, N.J., and was a 1942 philosophy graduate of Princeton University. He then served in Army intelligence in China during World War II.

He was an elder at National Presbyterian Church in Washington and a member of the St. Andrew’s Society, a Scottish heritage group. He did volunteer work for the National Alliance on Mental Illness.

A former Bethesda resident, he had lived the last nine years at Ingleside.

His wife of 57 years, Muriel Taylor Mackay, died in 2004. Survivors include three sons, Norman Mackay and Donald Mackay, both of Rocky River, Ohio, and D. Keith Mackay of Alexandria; two sisters; seven grandchildren; and four great-grandchildren.

— Adam Bernstein