In May 2010 basal stem rot of snake bean (long bean) (Vigna unguiculata subsp. sesquipedalis) caused by Sclerotium rolfsii was discovered in Vientiane Capital, Lao PDR, during an ad hoc disease survey. The disease had resulted in death of some infected plants. The basal stem region had a bleached appearance, a typical symptom of this disease. Abundant small, round, brown sclerotia were present on the stem base, and on the adjacent soil and dead leaf material. The fungus was isolated into pure culture and Koch’s postulates were fulfilled. This is the first report of S. rolfsii in the Lao PDR, and the first report of basal stem rot of snake bean caused by this pathogen in the Lao PDR.