Introduction: Field-In-Field (FIF) is a manually based forward Intensity-Modulated Radiation Therapy (IMRT) plan for which the calculated dose is modified in certain dose distribution areas by creating multiple lower-weighted reduction fields based on the primary field. The most common used form of FIF is the non-angled FIF, but if the inner subfield(s) is/are set at a different gantry angles from the major one, we will get a different design of the FIF technique, which is the angled FIF technique. Aim: The purpose of this study was to study the Angled Field-In-Field technique - as a new advanced form of FIF technique - and its related isodose lines shapes. Method: Using TPS and on the 2D-Array, a simple form of Non-Angled FIF (NAFIF) plan consists of 7×7cm2 field entire another larger 15×15cm2 field as a main field is designed on TPS. The two fields were set at the zero gantry position. Other FIF plan forms are designed in which the smaller inner field is set to (5°, 10°, 15°, 20° and 25°) gantry angles while the main field is fixed at zero gantry angle. The all FIF plans were verified using the 2-Dimintional Ionization Chamber Array (2D-Array) and its related Verisoft software. The Angled FIF, wedged and open fields were compared for studying their related isodose lines different shapes. Results: The results showed that the Angled Field-In-Field technique can be used as anew advanced technique for the radiotherapy and it has a new shape of isodose lines which is a stair shape. Future work: We predict that a Multiple-Angled Field-In-Field technique in which, the inner fields can be set at different angles in the same or reverse direction of the main angled field. This design has unknown isodose shape, but we predict that it can result in a semi-sloped stair shape, so it needs more study.