At the state oil company of Trinidad and Tobago, (Petrotrin) and its predecessor companies, Field Rejuvenation has evolved through time from single well targets to the more highly detailed and complex field reservoir characterization project currently underway. Initially single well target selection would be done by individual engineers operating their specific field. Generally, the benefit of these actions were not long term and did not significantly affect or arrest the declining production trends. At a more formal level there were studies undertaken in the process of the implementation a secondary or enhanced oil recovery project. This had the effect of arresting field declines and improving overall recoveries in the target fields. The foregoing activities were carried out by the operating companies of the day. In the late eighties because of limited capital resources, a program of leasing blocks of idle wells to small independent local operators was initiated. This program proved successful in increasing indigenous oil production from idle assets as well as generating positive cash flows. It was therefore expanded and has since included farmouts and joint-venture arrangements with foreign companies participating also. Currently Petrotrin is concluding a detailed field reservoir characterization study of one of its most mature fields on land which began production in 1913. The preliminary results have demonstrated the crucial role of reservoir characterization in evaluating the true potential of mature fields, and its potential for increasing production even from these fields.