This invention features ring-substituted pyrrolo-.beta.-carboline derivatives and ring-substitution and structural derivatives of 3-(1H-indol-3-yl)-1H-pyrrole-2,5-dione of formulas I III, which are useful as neuroprotective and anti-proliferative compounds. Also disclosed are methods for the preparation of these compounds, selected biological profiles and uses of these compounds in the treatment of various neurodegenerative and inflammatory diseases of the human nervous system and in the treatment of various other proliferative disorders characterized by loss of growth or cellular differentiation control including, but not limited to, cancer and inflammation. ##STR00001##