For activities that have a high possibility of causing environmental accidents, like in the oil and gas sector, it is reasonable to expect the environmental management to be an important variable within the companys strategic planning. However, this is not always true. In some cases, a change in the companies attitude, abandoning a reactive position and assuming a proactive one, only happens upon the occurrence of serious environmental accidents with strong repercussion in the media. For the company that was the object of study, these accidents gave rise to deep changes in its environmental management, culminating in investments of approximately US$ 2.6 billion in environment, health and security, from 2000 to 2004. This was the highest amount to date invested on these areas by an oil company. This case study seeks to discuss the integration between environmental management and strategic planning in the oil and gas sector over a period of 10 years (from 1995 to 2004) in order to make a contextual analysis of the period before and after the environmental accidents possible.