Among several viable explanations for the ubiquitous SES-health gradient is differential exposure to environmental risk. We document evidence of inverse relations between income and other indices of SES with environmental risk factors including hazardous wastes and other toxins, ambient and indoor air pollutants, water quality, ambient noise, residential crowding, housing quality, educational facilities, work environments, and neighborhood conditions. We then briefly overview evidence that such exposures are inimical to health and well-being. We conclude with a discussion of the research and policy implications of environmental justice, arguing that a particularly salient feature of poverty for health consequences is exposure to multiple environmental risk factors.