In February 1979, Cambodia signed a Treaty of Peace, Friendship and Cooperation with Vietnam that formally strengthened "solidarity and cooperation" between the two countries. As part of the Vietnamese aid program to Cambodia, a joint scheme of pairing Cambodian provinces with Vietnamese "sister provinces" was iÍÍÍÍnaugurated in the same year for the purposes of economic cooperation and of technical, educational and cultural exchange. Cambodia's Rotanokiri Province, however, was linked with two neighboring Vietnamese provinces--Nghia Binh and Gia Lai-Cong Tum. In addition, the municipality of Phnom Penh was paired with two Vietnamese cities--Ho Chi Minh City and Hanoi. Except for the municipalities of Hanoi and Haiphong, all of the Vietnamese participants in the scheme were located in former South Vietnam near their Cambodian counterparts (see fig. 1 table A).

The paired provinces were engaged mostly in barter trade the volume and value of which were unpublicized. Some observers argued that the system facilitated the integration of Cambodia's economy into Vietnam's. They pointed to the case of Batdambang Province, which sent tons of rice to its overpopulated and underfed Vietnamese sister province, Quang Nam-Da Nang, in exchange for bicycles and cement. In another case, Cambodia's Siemreab-Otdar Meanchey Province, supplied Vietnamese counterparts in Binh Tri Thien Province with unmilled rice and other agricultural products in return, Vietnam supplied workers from Hue and its suburbs to help run the building industry in Siemreab-Otdar Meanchey This exchange came at the expense of Cambodian workers, who were assigned to find clay, while the new Vietnamese settlers produced bricks and tiles and made a good living. In Siemreab city, the Vietnamese also assumed control of the biggest fish-sauce factory.

According to a Cambodian official's evaluation of foreign cooperation, the pairing system worked successfully. The exchange of goods between the sister provinces and cities helped "meet the needs of the people promptly." Reportedly, the system also helped Cambodia fulfill all of its development targets for 1986. In February 1986, Cambodia and Vietnam signed an agreement to double their trade for that year.

Data as of December 1987