MS3 Symposium Title: RESPIRE—The Guatemala Randomized Intervention Trial. Symposium Organizers: Kirk R. Smith, Nigel Bruce, and Byron Arana. MS3-01 Objectives: The objectives of this study were to site and conduct a randomized, controlled trial (RCT) to examine the improvement in child acute lower respiratory infection (ALRI) by introduction of a chimney stove designed to reduce indoor exposures to biomass smoke in a rural developing country setting. Background: After unsuccessful efforts in the 1980s to fund the RCT in Nepal, an international committee was established by WHO, Geneva, in 1991 to locate the best site for the RCT. Based on criteria related to local health, exposure, logistics, and institutional conditions, a dozen sites were examined in Asia, Africa, and Latin America. Highland Guatemala was chosen and a range of pilot studies undertaken in the 1990s to develop the data needed to design and successfully fund the RCT, which began in 2001. Setting: The chosen site is home to a largely indigenous primarily agricultural Mayan population living at 2700 to 3000 m in the western Guatemalan highlands. Most of the population speaks a local language, Mam, with Spanish as a second language for many. Nearly all households in the area use only wood for all household fuel requirements. Preintervention ALRI rates in young children were estimated at 0.5 per child-year. Methods: A rapid assessment was undertaken among 5500 households in the area to screen for recruitment based on use of an open fire for cooking, presence of a pregnant women or child under 4 months, migration patterns, and willingness to participate. To meet statistical goals (two-sided α = 0.05, power = 0.80, 25% effect), 534 households were eventually recruited, 518 (97%) of which contributed to the final dataset. After baseline household and indoor air quality (IAQ) surveys, households were randomly assigned to receive an improved chimney stove, the plancha, at the start of the study or at the end, when the study child reached 18 months, or a household dropped out. Pilot work showed that planchas were popular, sturdy, and capable of substantially improving kitchen IAQ. After stove installation, weekly household visits were conducted by trained fieldworkers to identify potentially ill children, who were then referred to study physicians (see companion abstract for details). Planchas were repaired by the study when structural problems appeared. Anthropometry was conducted regularly and birth weights recorded within 48 hours after delivery. Verbal autopsies were conducted on all child deaths. Quarterly personal 48-hour CO exposures were obtained for all study children and mothers. Intensive IAQ monitoring for CO and PM was conducted in a 13% subsample along with outdoor monitoring and assessment of exposures from use of wood-fired saunas (temascals). Results: The 518 children followed contributed nearly 600 child-years of surveillance. Randomization was successful because there were no significant differences between the 2 groups for any of the dozens of household, demographic, and social variables examined, except for leaks in the roof. At 8%, the dropout rate was within the 20% projected in sample-size calculations and was due primarily to migration (50%) from the area. There was a slightly higher dropout rate (9.3% P = 0.39) for intervention households. Discussion: Although not easily quantified, absolutely essential for successful implementation were the hospitality and cooperative spirit of the local communities and the field workers recruited from them.Table