S Stimulation is one of methods used for improving wells experiencing production decline caused by formation damage or by the presence of deposits in thewell. The stimulation methods used in this Final Project are matrix acidizing and well washing. Stimulation is intended to increase production from the wells affected by formation damage. The objects of this investigation are geothermal wells MBF – 246 with an enthalpy of 2784 kj/kg; and well MIZ – 153 with an enthalpy of 2700 kj/kg. A chemical production analysis on MBF – 246 indicated the presence of mineral deposits such as silicate or calcite, while a macroscopic analysis from sample catchers indicated the presence of unexpanded clay minerals in the form of lithic tuffs around the liner up to the fractures. These could be treated with acid injection using the matrix acidizing method. As for well MIZ – 153, the decline in production was due to the presence of calcite deposits with a saturation index of 1.807. These deposits surrounded the liner and production casing. They could be treated with a condensate injection using the well washing method. The aim of this study is to evaluate the effectiveness of matrix acidizing and well washing as well as their respective application on field. In order to assess the success of matrix acidizing and well washing stimulations, an evaluation is needed so that information regarding both the actual application on the field as well as the resultant increase in production can be obtained. For this reason, the present Final Project is given the title “EVALUATION ON THE SUCCESS OF MATRIX ACIDIZING AND WELL WASHING APPLIED TO GEOTHERMAL WELLS MBF – 246 AND MIZ – 153 ATWAYANG WINDU FIELD”. Evaluation on the success of matrix acidizing wasanalyzed using the parameters of injectivity index and production performance. As for well washing, the evaluation was assessed only using one parameter: production performance. The evaluation yielded the following results: matrix acidizing on geothermal well MBF – 246 managed to increase production capacity to 19 kg/s from a prestimulation production of only 14 kg/s. The well washing applied on MIZ – 153 managed to increase production to 28 kg/s. Before the well washing, this well managed to only produce a steam mass flow of 23 kg/s. The conclusion to be drawn from the evaluation is that both matrix acidizing and well washing stimulation methods are said to have successfully achieved improvement in wells MBF – 246 and MIZ – 153 marked by the respective increases in production post-stimulation.