Drawing on recently declassified American documents, this article traces the shift in U.S. policy toward the People's Republic of China (PRC) initiated by the Johnson administration in 1965–1966. During the first two years of his presidency, Lyndon Johnson resisted proposals to adopt a more flexible stance toward China, owing in large part to his suspicion that Beijing was encouraging and supplying the Communist insurgency in South Vietnam. This perception remained intact for the duration of the Johnson years and stifled major changes in policy toward China. Yet ironically, the Vietnam War itself led to a reappraisal of long-standing strategy toward the PRC. Johnson's determination to head off the threat of Chinese intervention in Vietnam and to sustain public support for the war yielded a relaxation of travel restrictions, the promotion of unofficial contacts between the two countries, and a striking change in rhetoric.