The Tzeltal Maya of Highland Chiapas have widespread generalized knowledge about medicinal plants and the biophysical environment. Medicinal plants play an overwhelmingly primary role in daily health care. Tzeltal self-administer treatments and rely on clinics and/or specialized healers on rare occasions for very serious conditions. Research was conducted in six communities distributed throughout the three major ecological zones in the municipality of Tenejapa to gather data regarding medicinal plant knowledge, use and procurement. Illnesses and medicinal plant treatments were tracked for 208 individuals for a period of 7 months. Data were collected regarding habitat, time allocation, distance, soil type, vegetation type, seasonality, efficacy, availability, use, treatment and admixtures. 122 plant species were utilized to treat a variety of ethnomedical conditions, with over 80 percent of the cases involving gastrointestinal and respiratory illnesses. 93 percent of medicinal plant procurement was conducted within a 2-km radius of the household, 71 percent within a 1km radius. The average time spent in procurement of medicinal plants was 16 minutes. The distribution of medicinal plants were analyzed within specific ecological zones based on land use and degree of human modification. 86 percent of medicinal plants were obtained in managed areas or areas of secondary vegetation (non-forest). 14 percent were obtained in young secondary forest. No medicinal plants were obtained in old secondary or mature forest. Tzeltal living within a 1-km radius of mature forest were also interviewed. None could recall obtaining medicinal plants in mature forest for any illness at any time yet they could recognize a set of mature forest obligate medicinal plants. Research was also conducted on the ecological distribution of 203 medicinal plants with the highest consensus as to their use. 2842 responses were recorded. Early successional stages were reported as the most common habitats for medicinal plants with distribution falling off sharply in forested areas. These findings support the main study. Explanations are presented based on evidence and theory from human ecology and biochemical ecology. Implications for general conservation, medicinal plant conservation, and the relationship between health and the biophysical environment in Chiapas, Mexico are discussed.