The preferred embodiments generally relate to methods and compositions that affect the GTP-binding activity of members of the Rho family GTPases, preferably Rac (Rac1, Rac2 and/or Rac3), such compositions include compounds that modulate the GTP/GDP exchange activity, along with uses for the compounds including screening for compounds which recognize Rac GTPase, and methods of treating pathological conditions associated or related to a Rho family GTPase, including Rac. The preferred embodiments also relate to methods of using such compounds, or derivatives thereof, e.g., in therapeutics, diagnostics, and as research tools.