Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S. ; Journal Article ; Research Support, N.I.H., Extramural ; Multicenter Study ; OBJECTIVE: A recent randomized clinical trial demonstrated home-based treatment of WHO-defined severe pneumonia with oral amoxicillin was equivalent to hospital-based therapy and parenteral antibiotics. We aimed to determine whether this finding is generalizable across four countries. METHODS: Multicentre observational study in Bangladesh, Egypt, Ghana and Vietnam between November 2005 and May 2008. Children aged 3-59 months with WHO-defined severe pneumonia were enrolled at participating health centres and managed at home with oral amoxicillin (80-90 mg/kg per day) for 5 days. Children were followed up at home on days 1, 2, 3 and 6 and at a facility on day 14 to look for cumulative treatment failure through day 6 and relapse between days 6 and 14. RESULTS: Of 6582 children screened, 873 were included, of whom 823 had an outcome ascertained. There was substantial variation in presenting characteristics by site. Bangladesh and Ghana had fever (97%) as a more common symptom than Egypt (74%) and Vietnam (66%), while in Vietnam, audible wheeze was more common (49%) than at other sites (range 2-16%). Treatment failure by day 6 was 9.2% (95% CI: 7.3-11.2%) across all sites, varying from 6.4% (95% CI: 3.1-9.8%) in Ghana to 13.2% (95% CI: 8.4-18.0%) in Vietnam; 2.7% (95% CI: 1.5-3.9%) of the 733 children well on day 6 relapsed by day 14. The most common causes of treatment failure were persistence of lower chest wall indrawing (LCI) at day 6 (3.8%; 95% CI: 2.6-5.2%), abnormally sleepy or difficult to wake (1.3%; 95% CI: 0.7-2.3%) and central cyanosis (1.3%; 95% CI: 0.7-2.3%). All children survived and only one adverse drug reaction occurred. Treatment failure was more frequent in young infants and those presenting with rapid respiratory rates. CONCLUSIONS: Clinical treatment failure and adverse event rates among children with severe pneumonia treated at home with oral amoxicillin did not substantially differ across geographic areas. Thus, home-based therapy of severe pneumonia can be applied to a wide variety of settings.