Dr. Ben D. Dorfman, 83, an authority on international trade who was a chairman of the old U.S. Tariff Commission in the Kennedy and Johnson administrations, died Sept. 30 at the Alvarado Nursing Hospital in San Diego. He had cancer.

Dr. Dorfman made his career at the commission, whose function was to adjudicate American industry's claims for protection from foreign imports. He began in 1934 as a senior economist. In 1943 he was named chief economist and in 1951 took on additional responsibilities as chief of the economics division. He held both posts until 1961, when President Kennedy nominated him chairman. He headed the agency until 1965, when he tendered his resignation to President Johnson for reasons of health.

When Dr. Dorfman became chairman, the agency, which is now the U.S. International Trade Commission, was taking a generally protectionist line. This ran counter to the view of the Kennedy administration that international commerce was essential to the rising prosperity of the noncommunist industrialized world, including West Germany and Japan. To promote trade the administration was willing to cut tariffs even if less agile industries and economic groups were hurt.

The results included the Trade Expansion Act of 1962, which gave the president wide powers to negotiate tariff reductions, and the Kennedy Round of talks on the General Agreement on Trade and Tariffs (GATT). The economic dislocations caused by these developments set the political context in which the Tariff Commission did its work.

International trade engages highly technical questions. Dr. Dorfman's mastery of these technical matters was an important factor in his appointment. Another consideration was his sympathy for the broad goals of the Kennedy administration and his ability to resist pressure from special interests.

A recurring issue during his chairmanship was "adjustment assistance." This arose under the Trade Expansion Act, which under certain circumstances allowed the "adjustment" of tariffs to protect industries and employe groups from increased imports.

In Dr. Dorfman's first 18 months in office there were five appeals for "adjustment assistance" and all were turned down. This drew what an editorial in The Washington Post described as "a barrage of wholly unjustified criticism." The editorial went on to say that in none of the cases "could there be demonstrated a reasonable connection between losses of employment or sales and an increase in imports."

When Dr. Dorfman resigned, The Post urged President Johnson to "bend every effort" to retain his services. "At a time when the future of world trade may well hinge on the skill with which this country conducts its trade policies," the editorial said, Dr. Dorfman "is far too valuable a man to lose."

A native of Portland, Ore., Dr. Dorfman graduated from Reed College and received master's and doctoral degrees in economics at the University of California at Berkeley. He taught there and at the universities of Hawaii and North Dakota. In 1932, he was an economic adviser to the Lytton Commission of the League of Nations, which investigated the Japanese takeover of Manchuria. He moved to Washington in 1934 to begin his work at the Tariff Commission.

Dr. Dorfman worked with several bodies concerned with the economics of the Philippines and Puerto Rico in the 1930s and 1940s. During World War II, he was a liaison officer with the Board of Economic Warfare and worked at various periods for the War Production Board. Over the years he attended numerous conferences on international trade.

Dr. Dorfman was a member of the American Economic Society and the Cosmos Club. He lived in Washington until moving to San Diego in 1982.

His wife, the former Hilda Rotenberg, died in 1974. Survivors include two children, David H. Dorfman of San Diego and Harriet Reisman of San Francisco, and four grandchildren.