Provided are methods for screening for drugs effective for treating fibrotic conditions. One screening method comprises exposing a cell to a test compound, monitoring the effect of the test compound on the amount or form of a cell molecule, comparing the amount or form of the cell molecule with the result obtained by treatment of the cell with an anti-fibrotic -effective amount of a withanolide compound, and selecting a drug effective for treating a fibrotic disease based on the ability of the test compound to provide the effect obtained by the withanolide compound on the cell molecule. Also provided is a method of treating a fibrotic disease comprising administering an anti-fibrotic effective amount of a withanolide compound to a mammal in need of treatment for fibrosis
