Background: “Frailty” has emerged as a condition associated with an increased risk of functional decline among the elderly, which may be differentiated from aging, disability, and co-morbidities. Objective: The Mexican Study of Nutritional and Psychosocial Markers of Frailty among Community-Dwelling Elderly has emerged to help answer many questions about frailty among the older adults. This report presents the design of the study and baseline data of its participants. Design. The “Coyoacan cohort” is a longitudinal observational study developed in Mexico City. Participants: A representative sample of 1,294 non-institutionalized men and women aged 70 years and older were randomly recruited to undergo a face-to-face interview and a comprehensive geriatric assessment (including clinical evaluations and blood samples) between 2008 and 2009. Measurements: Data collected included socio-demographic and economic characteristics, medical history, oral health, drug use, cognitive function and mood, nutritional status, physical performance and functional status, physical activity, quality of life, social networks, and biological data. Frailty was defined as the presence of ≥3 of the following components: slowness, poor muscle strength, low physical activity, exhaustion and unintentional weight loss. Results: A total of 1,124 participants completed the interview. The mean age was 79.5 ± 7.1 years, and 55.9% were female. Nine hundred and forty-five subjects completed the clinical evaluation and 743 blood samples were collected. The baseline prevalence of frailty was 14.1%. Conclusions: Understanding the medical, biological, and environmental factors that contribute to the phenomenon of frailty is the goal of the current research in the field.