The major cause of death in the world is cardiovascular diseases. A primary risk factor for the disease is known to be hypercholesterolemia. Lovastatin (also known as mevinolin, monacolin K and Mevacor™) is a valuable hypocholesteremic drug, which inhibits biosynthesis of cholesterol by competitively inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase). Lovastatin was produced by Aspergillus terreus strain ATCC 20542 at a little amount, but the main product was menvinolinic acid which was lactonized into lovastatin in the presence of a hydrophobic solvent. In the present study, the authors isolated acid menvinolinic from the fermentation broth of A. terreus ATCC 20542 and investigated on factors including pH, temperature, time, purity of menvinolinic acid and organic solvents affecting the lactonization. Crude acid menvinolinic was isolated and purified using preparative medium pressure liquid chromatography (MPLC) and high pressure liquid chromatography (HPLC) with a separation efficiency of 30 percent and a purity of 70 percent. Optimal conditions for the lactonization reaction was observed at pH from 3.4 to 3.6, 40°C to 60°C, 12 hours for reaction, and in toluene.