Mistotoe (Tapinanthus globiferus) as freshly prepared leaf extract was administered at variable concentration (25, 50 and 100 mg/kg) per body weight as dietary supplement to laboratory albino mice via oral gavage for two weeks consecutively. The mice were also simultaneously administered 1.5 mg/kg pesticide precursor (Prontosil). 24 hours after the last day, the mice were sacrificed and chromosome preparations were made from the bone marrow cells. The end-points studied were polychromatic erythrocytes and damage cells. The results indicated that the clastogenicity in the mice fed with Tapinanthus globiferus leaf extract reduced significantly (P<0.05) compared to those fed with prontosil only. The marked reduction of clastogenicity by the extract may be attributed to the interaction with polyphenolic and phytochemical components of the extract.