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The purpose of this study is to find out the dosimetric parameters of electron beams for the usage of asymmetric fields, and checks the accuracy of treatment planning system. A GE CGR Saturne-42 model linear accelerator which produces dual photon energies of 6 and 15 MV, and eight energies of 4,5, 6, 7,5, 9, 12, 15, 18, 21 MeV. 6 and 15 MeV electron energies and an ISIS 3D TPS were used in this study. Percent depth doses(PDDs), dose profiles, and isodose distributions for symmetric and asymetric fields were generated in a water phantom. The results are compared with dosimetric characteristics of electron beams from ISIS 3D TPS in clinical use. It has been seen that the asymmetric fields can be used in the clinics.