Mycelium of Hericium erinaceum isolate KU-1 was cultured in liquid medium (HL medium) and solid medium (Ko medium) at pH 4.0 in 28°C. 1.0% glucose or fructose was the most favorable carbon source, and 0.2% amonium acetate or NaNO3 was an exellent nitrogen source for mycelial growth as well as production of antimicrobial substances. The mixture of saw dust 70% with rice bran 30% (SR medium) was the substrate for formation of sporophores. The active substrates in extracts from mycelium, culture filtrate and fruiting body were separated by TLC. The solvent for TLC was EtOAc : Chloroform : MeOH (10:5:10). Phenol-like substances appeared at Rf 0.5~0.9, and fatty acid-like substances appeared at Rf 0.1~0.2. The purified materials from the extracts showed antimicrobial effects to Escherichia coli, Bacillus subtilis, Staphylococcus aureus, Aspergillus niger, Candida albicans and Microsporum gypseum. The S. aureus was the most inhibited. Minimal inhibitory concentration (MIC) of purified white powder and the Hercenone derivatives against S. aureus were 5.65 μg/ml and 1.85 μg/ml, respectively.