Pestalotiopsis microspora is an endophyte associated with many plants including Taxus wallachiana. Isolates commonly produce taxol in liquid culture. Defining culture amendments to optimize taxol production by P. microspora is a critical step toward the realization of fungal taxol for treating human cancers. The lowering of phosphate and the addition of sodium benzoate in the medium increased taxol production. Sterol biosynthesis inhibitors, such as tebuconazole and triadimefon, dramatically increased taxol yields.