Recent large-scale outbreaks in the Lao People's Democratic Republic (Lao PDR) were reported in 1993 and 1994 and from 2000 to 2002. On December 23, 2007, a drastic increase in acute watery diarrhea patients at a health center in Sekong Province was reported to the provincial health office. An outbreak investigation was initiated to understand the magnitude of the outbreak, identify new cases, identify the suspected causal agent, implement control measures, and prevent new cases. Through active village based surveillance, 370 cases and 3 deaths were reported from 31 villages between December 15, 2007 and January 29, 2008. Of these reported cases, 29% were under the age of 5. From 28 fresh stool samples taken, 17 (58.6%) were positive for Vibrio cholerae O1 Ogawa strain. Two water sources close to affected villages were found to be contaminated with the same strain of V. cholerae. Control measures implemented included health education for safe household water consumption and early identification and treatment of suspected cholera patients at village level. The cause of the outbreak was suspected to be a combination of contaminated drinking water and person-to-person transmission.