The EsMaestras study is a prospective cohort study which enrolled female teachers 25 years and older from 12 states of Mexico including urban and rural schools. The main objective of the cohort is to evaluate life styles and environmental risk factors related to chronic diseases with major focus on breast and reproductive cancers, diabetes and cardiovascular disease in a society with rapidly changing life styles, increasing sedentarity and westernized diet. The main exposures of interest are dietary intake, physical activity, obesity and environmental exposure in particular endocrine disruptor chemicals as well as gene by environment interaction. The study started in 2006 enrolling teachers from 2 states (Veracruz and Jalisco) in 2008–2009, 10 others states were included. To date the study enrolled close to 116 000 women. Overall the response rate has been 64%, and follow-up at 4 years 71%. Information on sociodemographic, lifestyle, reproductive history, medical history, anthropometry, physical activity and diet is collected through biennial questionnaire. In addition in a subsample of the study population detailed information including mammographic density, bone density, blood pressure, spirometry, impedance and anthropometric measurements, blood and urinary samples as well as more detailed questionnaire on lifestyle. This large cohort with a high variability in lifestyle and fast changing habits will provide very valuable information on risk factors of chronic diseases in female.