Vientiane, as a capital city, is unlikely to be representative of this ethnically and geographically diverse country. We are therefore studying the causes of fever at rural sites outside the capital. We support a blood culture service, with the flying and busing of culture bottles to Vientiane from Luang Nam Tha Provincial Hospital, in northern Laos, and Attapeu and Salavan Provinicial Hospitals in southern Laos, with a major aim being to prospectively document changes in the antibiotic resistance pattern of S. typhi. We are examining the causes of fever, particularly rickettsial diseases, dengue, leptospirosis and Japanese encephalitis infections, and the prevalence of thiamine deficiency among the inhabitants of Xienglekok, in southern Laos. We hope that this work will allow some conclusions on the disease burden in rural Laos, where 80% of the population live.