This practice note provides you and your clients with an overview of the federal environmental regulation affecting the oil and gas exploration and production (E&P) industry. There is substantial environmental regulation of oil and gas E&P at the federal and state levels through the Environmental Protection Agency (EPA) and other agencies. Although it is estimated that states conduct between 80 and 90% of all enforcement actions affecting the E&P industry, these actions are often taken based on federal environmental regulations. For the purposes of providing state examples, we have used Texas as the model here. The practitioner should recognize that the rules do vary by state, as the federal government has left a lot of the enforcement of the federal laws to the states, and the states in turn, have incorporated portions of the federal laws into their own, while adding others as well.