The present invention provides a screening method for identifying test agents that modulate cell membrane cholesterol activity. The modulating activity of the test agents may be measured using lytic compounds, which cause cell lysis or increases in cell permeability in response to cell membrane cholesterol levels. The invention further provides therapeutic agents that are identified using the screening method. The therapeutic agents either increase or decrease the cell membrane cholesterol activity, cholesterol concentration and/or both in vivo and/or in vitro.