Summary This paper summarizes the major U.S. and State of California environmental regulations relevant to thermal EOR processes and assesses their impact on the process. The environmental laws that have the greatest impact on thermal EOR processes pertain to air quality, water processes pertain to air quality, water quality, hazardous wastes, and environmental quality. This paper also identifies the source and type of pollutant likely to be generated in a pollutant likely to be generated in a typical thermal EOR facility. Introduction In recent years, thermal EOR operators have faced increasingly stringent environmental regulations oriented toward preventing significant degradation of air and water quality and land misuse. These environmental laws and regulations significantly affect the design and operation of thermal EOR processes. U.S. federal, state, local agencies are involved in the enactment and implementation of various environmental laws and regulations. Because jurisdictions frequently overlap, confusion can occur. For example, in California both the Dept. of Health Services and the Regional Water Quality Control Board may be involved in determining the level of cleanup of old oilfleld sumps and in improvements. The reason is that the Dept. of Health Services regulates hazardous wastes while the Regional Water Quality Control Board regulates any waste placed on land that may affect water quality. Although a company's environmental specialists may be familiar with environmental laws and regulations and aware of the agencies responsible for enforcing them, other personnel may not have that knowledge. Technical and operating personnel responsible for reporting actions must also be aware of these regulations to avoid inadvertent noncompliance with applicable environmental rules and regulations. The purpose of this paper is to familiarize thermal EOR practicing engineers and other interested personnel with applicable environmental rules and regulations. The paper provides a summary review of may but not all, environmental laws ad regulations that could be applied to thermal EOR facilities ad operations. The environmental laws that have the greatest impact on thermal EOR processes pertain to air quality water quality, processes pertain to air quality water quality, hazardous wastes, and environmental quality. In California, separate federal, state, and often regional or local laws and regulations pertain to these environmental areas. Because pertain to these environmental areas. Because California is the hub for thermal EOR operations in the U.S., California regulations are emphasized. The applicable regulations for those states where thermal EOR is being implemented, or is likely to be implemented, are summarized elsewhere. The material in this paper was assembled by consulting publications of various federal, state, and private organizations. While every attempt was made to acquire the most recent applicable regulations or standards, regulatory processes are constantly evaluated, ad the processes are constantly evaluated, ad the findings presented here may not be current. At best, the information presented here was applicable up to late 1990. Furthermore, because the interpretations and enforcement standards in various regions can and do differ appreciably, the future potential constraints to thermal recovery processes cannot be defined readily.