Postpartum haemorrhage is a major cause of maternal mortality in the developing world. Although effective methods for prevention and treatment of such haemorrhage exist--such as the uterotonic drug oxytocin--most are not feasible in resource-poor settings where many births occur at home. We aimed to investigate whether oral misoprostol, a potential alternative to oxytocin, could prevent postpartum haemorrhage in a community home-birth setting. In a placebo-controlled trial undertaken between September, 2002, and December, 2005, 1620 women in rural India were randomised to receive oral misoprostol (n=812) or placebo (n=808) after delivery. 25 auxiliary nurse midwives undertook the deliveries, administered the study drug, and measured blood loss. The primary outcome was the incidence of acute postpartum haemorrhage (defined as > or =500 mL bleeding) within 2 h of delivery. Analysis was by intention-to-treat. The trial was registered with the US clinical trials database (http://www. clinicaltrials.gov) as number NCT00097123. Oral misoprostol was associated with a significant reduction in the rate of acute postpartum haemorrhage (12.0% to 6.4%, p<0.0001; relative risk 0.53 [95% CI 0.39-0.74]) and acute severe postpartum haemorrhage (1.2% to 0.2%, p<0.0001; 0.20 [0.04-0.91]. One case of postpartum haemorrhage was prevented for every 18 women treated. Misoprostol was also associated with a decrease in mean postpartum blood loss (262.3 mL to 214.3 mL, p<0.0001). Postpartum haemorrhage rates fell over time in both groups but remained significantly higher in the placebo group. Women taking misoprostol had a higher rate of transitory symptoms of chills and fever than the control. Oral misoprostol was associated with significant decreases in the rate of acute postpartum haemorrhage and mean blood loss. The drug's low cost, ease of administration, stability, and a positive safety profile make it a good option in resource-poor settings.