The overall view of this project is to study the behavior of cold formed steel channel section beams with an infill of concrete. The flexural behavior of cold formed steel in filled and hollow beams is investigated by conducting experimental study using two point load test. Totally twelve beams are tested, out of which six are in filled with concrete and remaining six are hollow sections. Depth to thickness ratio is varied from 45 to 75 for all sections. For comparison, theoretical values are calculated based on Rigid Plastic Analysis for in filled beams and Australian/ New Zealand code 4600-2005 for hollow sections. Tremendous increase in load carrying capacity of in filled sections is observed. Using same amount of steel, high strength was attained by filling the sections with concrete.Experimentally it is observed that the load carrying capacity for in filled beams is not affected with a flat width ratio up to 71 for depth of section. The objective of the study is to investigate cold-formed steel rectangular hollow sections beams with respect to strength, stiffness and ductility and load deflection behavior and to predict the behavior of beams in full-scale structures. The entire study is divided in to two distinct phases of activity. In the first phase, the Properties of materials were studied and experimental were conducted on ingredients and also to analyses the mix design of concrete.