Transformer reliability is in direct connection with condition of transformer insulation system. In other words, operation safety of transformer in not affected as long as transformer insulation is in good condition. The most common insulation system used in transformer is oil-celulose system. Higher temperatures during service load accelerate degradation of insulation and directly influence on reduction of transformer life-time expectancy. Temperature rise test simulates the most severe service load situation regarding thermal condition of tranformer, determines maximum oil and winding temperatures and as a result can be used as functional test and also proof-test of good dimensioning of transformer cooling system. This paper gives an overview of testing methods that can be used for performance of temperature rise test. Paper gives detail description of heat run test done by 'short circuit' method, which is proven to be the most practical and therefore most commonly used method. Also, a recommendation is given on applying of additional testing methods along with temperature rise test. Temperature rise test is defined by standard IEC 60076-2 ( 1993-04 ), and new standard is being prepared. By now, only 'first draft' of new standard IEC 14/563/CD ( 2007-08 ) is published, and also a comparison of old and new standard is given. Heat run test is long-run test during which a great amount of measuring data is collected. To determine the required heating values, measured data must be processed. Processing itself is a thorough, long-lasting and complex process. For that reason a programming support with detail mathematical model is also given. Data processing program itself is written using Excel program package, following the presumption that Excel is a program package majority of users is familiar with. Also, Excel is compatible with data taken by measurement instruments, making input simple and allowing quick processing of great numbers of input data. It also allows quick processing of semi-results during the temperature rise test, which is a result of need for evaluation of final results as early as possible.