The mutagenic activities of the pyrolysates(300, 600, 750 and 85$0^{circ}C$) of extracts from four antitussive or expectorant medicinal plants(Daturae Folios, Scopoliae Rhizoma, Acori Rhisoma, and Schigandrae Fructus) were studied in the Ames Salmonella/microsomes test system. The pyrolyzate of Schizandrae Fructus did not show the mutagenicity to tester strain TA98 of Salmonella typhinurium. However, those of other medicinal Plants, Daturae Folium, Scopoliae Rhigoma and Acori Rhizoma, exhibited the mutagenic activity to this strain and the mutagenicity of them were decreased gradually to 70% of the initial activity according to time course after the preparation of the samples with DMSO.