Early planning for a meeting in space took place in 1969. A formal agreement between the United States and the Soviet Union was signed in May of 1972.
The Soviet side of the project consisted of several launches, the first two being unmanned tests of the modified Soyuz systems. The two unmanned flights were given the Cosmos designation.
Cosmos 638 - 3-13 April 1974
Cosmos 672 - 12-18 August 1974
While ASTP was a sign of an easing of cold war tensions, it would be another ten years before there was any real sharing of technologies.