Well-designed hybrid structures can combine the different performance strengths of each material. This guide focuses on design approaches for concrete structures reinforced in an unconventional way by steel profiles. It explains force transfer mechanisms at steel profile-concrete interfaces and the peculiarities of the analysis of hybrid structures, including slender members. Several types of hybrid designs are addressed: walls and columns with several embedded steel profiles, connections strengthened by steel profiles between steel, and composite or reinforced concrete members, including the specific case of shear keys connecting deep beams or flat slabs to columns. The transition zones in partly RC and partly composite columns are also covered. Design of Hybrid Structures draws on the European Smartcoco research project, of experimentation and numerical modelling, giving practical guidance for designers and introducing the subject for researchers and graduate students.