Use of steel bracing system to provide additional strength and stiffness to existing structures, especially those of reinforced concrete, is a relatively new concept. Little information is available on the behavior of frame-bracing systems and on rational procedures for the design of added bracing. Thus, a one-bay two-story two-thirds scale reinforced concrete frame with an added steel bracing system was tested under reversed cyclic deformations. The bracing system consisted of ductile braces in an inverted V-pattern, and horizontal and vertical members (Collectors). The strengthened frame showed excellent hysteretic behavior under a large number of cyclic deformations up to 3% of story drift. The hysteresis loops of the strengthened frame were very "full" and stable with a dramatic increase in energy dissipation capacity. An analysis of story shear forces showed that a significant portion of added strength was provided by the steel collectors in addition to that provided by the braces.