The currency of Laos is the Kip. The Kip is not freely convertable, which means that you can't get it outside of Laos, and any you leave with can't be exchanged.
The Kip is not very stable, but fluctuates widely around the 10,000 Kip per US$1 mark. For the purposes of this guide, we've shown approximate rates using this figure. At current exchange rates, one USD is worth 0.86 LAK.
Kip notes come in 1,000, 2,000, 5,000, 10,000, 20,000 abd 50,000 denominations. There are no coins. Many larger purchases may be made with US Dollars or Thai Baht. You just need Kip for small purchases like entrance fees, taxis and meals.
Ye olde ATM in Luang Prabang, Laos
Most tourist centers will have bank operated exchanges where you'll get the best rate. These will most typically be open until the early evening hours and on Saturdays. There are also many ATMs in Vientiane and Luang Prabang.