Penicillium digitatum (P. digitatum) is a pathogenic fungus mildewed fruits and its process products. There were some events of poisoning on the clinic because fruits and its process products mildewed by the fungi are eaten. A lot of reports were about the study on acute poisoning on this hand. But there were few reports about the study on genetoxicity, and therefor we determined the mutagenicity of P. digitatum with different methods to provide scientific basis for prevent the effect of human genetoxicity. METHODS: ① The preparation of extract from P. digitatum: Preponderant fungus separated from mildewed fruits was incubated in the Czapak's medium for two weeks, and then it was extracted with CHCL2 and evaporated. It was dissolved by dimethylsulfoxide (DMSO) for use. ② Bacterial reverse mutation assay: The assay was without S9 mix. E. coli ND-160 strain was used in the assay. The assay set up negative control, positive control and test group, The test group contained four concentrations (3.125 mg/plate, 6.25 mg/plate, 12.5 mg/plate and 25 mg/plate). ③ Micronucleus assay of polychromatic erythrocytes (PCE) in mice bone marrow. The assay was individed into negative control group (0.9% NaCl, 20 ul/mice), positive control group (cyclophosphamide, CP, 30 mg/kg B.W.) and test group (extract, 250 mg/kg B.W.). ④ Unscheduled DNA synthesis (UDS) assay in primary cells of lung and liver of rat. Fresh cells separated from lung and liver were incubated. There were three groups in the test. They were negative control group SO, 1%(v/v)], positive control group (10-7 mol/L 3-MC for lung cell; 10-7 mol/L HN2. HCL for liver cell). The radioactivity of cells that were treated was detected. The result showed unscheduled incorporation index, and the index represented the level of UDS. ⑤ Mutation assay in E. coli K12 infA gene. Using E. coli K12 strain as mutation target, partial infA gene was amplified by PCR, and the overlapping fragments were cloned into PGEN-T vector. Seqences were determined and then analyzed by computer. RESULTS: ①The extract remarkblely induced the reverse mutation of E. coli ND-160 strain and there was a linear dosage-effect relation. ②The extract significantly increased the micronucleus rate of mouse bone marrow (P<0.01). ③The extract could induced UDS in the primary cells of the lung and liver of rat, and UDS was particularly obvious in the primary cell of lung (P<0.01). ④Five point mutations in nucleotide of infA gene were induced by the extract, and one of them led to amino acid variation (Lys-Val). CONCLUSION: P. digitatum could cause gene mutation and eating mildewed fruits and its process products should be avoided.