ISEE-877 Introduction: Mexico has favorable environmental conditions for the development of climate-sensitive diseases according to characteristics of local geography and social conditions; however there are no previous studies that assess the potential effects of climatic change in human health in this country. As part of the Third National Communication of Mexico to the United Nations Framework Convention on Climate Change we developed the first formal assessment of the effects of climate change on health. Objective: To characterize the potential effects of climatic change in human health in Mexico, in order to help the decision makers to design and implement national strategies and policies for adaptation and mitigation. Material and Methods: The characterization is based upon a review of literature and the plausibility of the incidence of diseases associated with climate change in Mexican population. We used morbidity (1998–2004), mortality (1979–2004), and climatic data. Pearson correlation coefficients for monthly values of deaths, and mean, maximum, and minimum temperature were calculated. Poisson regression models were further performed to estimate the associations between mortality and climate. Results: Our findings suggest that heat-related mortality is estimated to rise significantly in the states of Sonora 1.35% and Baja California 1.29% when the maximum temperature increases by 1°C. The monthly mean temperature was shown to be the best indicator of the impact of climate on morbidity by acute diarrhea disease in Chiapas and Puebla; and in some South Mexican States we found an increase in the incidence of Vector Borne Diseases. Conclusions: This is the first attempt to create a diagnostic of the effects of climate change on the Mexican population's health. There is a need to generate knowledge about climate and its effects on human health in order to mitigate our vulnerability to this phenomenon.