This chapter focuses on some of the environmental and nutritional diseases and their causes. Tobacco smoking is the most prevalent and preventable cause of disease and death. The harmful effects of smoking pipe and cigar are somewhat less. Long-term smokers of filter-tipped cigarettes appear to have 30-50% lower risk of development of cancer due to reduced inhalation of tobacco smoke constituents. The harmful effects of smoking are related to a variety of factors, the most important of which is dose of exposure expressed in terms of pack years. Some of the tobacco related diseases are coronary heart disease, cancer of the lung and chronic obstructive pulmonary disease. Chronic alcoholism is defined as the regular imbibing of an amount of ethyl alcohol that is sufficient to harm an individual socially, psychologically or physically. Hypothermia may cause focal injury as in frostbite, or systemic injury and death as occurs on immersion in cold water for varying time. Some of the nutritional diseases are obesity, starvation, and protein- energy malnutrition and vitamin deficiency diseases. Marasmus is starvation in infants occurring due to overall lack of calories. Night blindness is usually the first sign of vitamin A deficiency. Deficiency of vitamin D causes rickets in growing children from 6 months to 2 years of age.