The present book shows the following: (1)An example of a quality assurance procedure of the 3D-planning system in some physical aspects such as block fields, wedged fields, MU calculations and in homogeneity corrections. (2)An example of a quality assurance procedure of the 2D-planning system in some physical aspects such as MU calculations and in homogeneity corrections. (3)A conventional 2D-TP was compared to 3D-TP for 10 patients with breast and bladder cancer. Both types of treatment planning were performed with two tangential fields for patients with breast cancer and 3-fields technique ( anterior & 2 lateral ) for bladder cancer patients. (4) The number of calculation planes sufficient for three dimensional treatment planning for radiation therapy of intact breast. Close agreements between the calculated and measured results were obtained for the 3-D treatment planning (Helax-TMS) for blocked field.The (3D) treatment planning system used in this work was the Helax- TMS version 5.1B from Helax AB based on a differential pencil beam model. The other (2D) treatment planning system, introduced in this study was the Multi data treatment planning system version 2.35."