Auxotrophs and drug resistant mutants from the mycelia of Lentinus edodes were obtained by UV irradiation at survival rates of $0.024{sim}2.45%$ and ethidium bromide (EtBr) enrichment after UV irradiation. The mutation rate was 0.40%, and back mutation rate was $4.81{ imes}10^{-4}{sim}8.46{ imes}10^{-4}$. Various amino acid-, nucleic acid-, and vitamin-requiring auxotrophs were isolated. The concentrations of several fungicides, antibiotics and amino acid analogues inhibiting the growth of L. edodes were determined. The MIC values for cycloheximide, benomyl, and p-fluorophenylalanine were 2, 2000, and 1000 ug/ml respectively. Five p-fluorophenylalanine-resistant mutants and eight benomyl-resistant mutants were selected by UV irradiation.