The Steel Slit Panel Frame (SSPF) system is a new Seismic Force-Resisting System (SFRS) intended for areas of high seismicity. The main components in an SSPF are: steel beams and columns, and Steel Slit Panels (SSPs). SSPs are steel plates with rows of vertical slits cut at equidistant spaces. Links (small columns) are formed between the slits. When the panel is subjected to shear load, these links behave as beams in double curvature, reaching their plastic moment capacity at both ends. Beams are simply connected to the columns in the SSPF. The SSPs provide all the stiffness, strength and energy dissipation in the system. This paper presents the design of the SSP and the SSPF system. This paper also presents two prototype buildings which were designed for a site in Los Angeles, California. Finally, a simplified model developed for analyzing SSPs is presented.