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SummaryFew studies have formally examined the relationship between meteorological factors and the incidence of child pneumonia in the tropics, despite the fact that most child pneumonia deaths occur here. We examined the association between four meteorological exposures (rainy days, sunshine, relative humidity and temperature) and the incidence of clinical pneumonia in young children in the Philippines using three time series methods: correlation of seasonal patterns, distributed lag regression, and case-crossover. Lack of sunshine was most strongly associated with pneumonia in both lagged regression (RR for a 1 hour increase in sunshine per day was 0.67 (95%CI 0.51 to 0.87)) and case-crossover analysis (OR for a 1 hour increase in mean daily sunshine 8 to 14 days earlier was 0.95 (95%CI 0.91 to 1.00)). This association is well known in temperate settings but has not been noted previously in the tropics. Further research to assess causality is needed.4