A methanol extract of Dictamni Radicis Cortex exhibited a mutagenic effect on Salmonella typhimurium TA100 and TA98 with S9 mix. Two mutagenic compounds in Dictamni Radicis Cortex were isolated on a Sephadex LH 20 column and silica gel column chromatography and by preparative TLC. These were identified as dictamnine and gamma-fagarine by UV, EI-Mass, 1H-NMR. Dictamnine and gamma-fagarine were mutagenic in strain TA100 and TA98 with S9 mix. The dose-response curves were linear in the range 10-40 micrograms. Dictamnine and gamma-fagarine had specific activities (His+/microgram) of about 50-70 revertant colonies in strain TA100, while in strain TA98 there were about 30-50 revertant colonies.