Most of the western border of Laos is demarcated by the Mekong River, which is an important artery for transportation. The Khong falls at the southern end of the country prevent access to the sea, but cargo boats travel along the entire length of the Mekong in Laos during most of the year. Smaller power boats and pirogues provide an important means of transportation on many of the tributaries of the Mekong.

Inland waterways, including the Mekong River, constitute the second most important transport network in the country. There are about 4,600 kilometers of navigable waterways, including sections of the Mekong, the Ou, and nine other rivers. The Mekong accounts for about 1,330 kilometers of the total navigable length. Although the Mekong flows through Laos for approximately 2,030 kilometers, it is only navigable for about 70 percent of this length, mainly because of rapids and low water levels in the dry season. Between Vientiane and Savannakhét, the river can accommodate boats with between seventy and 140 deadweight tons; otherwise it can carry between fifteen and fifty deadweight tons, depending on the season. Residents of lowland villages located on the banks of smaller rivers have traditionally traveled in pirogues for fishing, trading, or visiting up and down the river for limited distances.

Both public and private trade associations handle river traffic, including the State River Transport Company, based in Vientiane. In mid-1987 the State Water Transport Company had thirty-seven boats, most built with help from Vietnam. There are state warehouses at Savannakhét, Xénô, and Vientiane, in addition to a number of ports. River transportation has improved as government policy has emphasized expanded trade with Vietnam and with rural regions.