Abstract: Four antimalarials, pyronaridine, chloroquine, quinacrine, primaquine, and two an-tifilarials, furapyrimidone, phenthiourezine (I) were administered to groups of Kunming hybrid male mice at ≥LD50 doses. Giemsa stained bone marrow cell smears of the mice were made 24 h after administration and the micronulceated polychromatic erythrocytes pel 1000 polychromatic erythrocytes (MNPCE % ) were counted. The MNPCE %?of each mouse in the six drug groups was 4‰, within the range of the controls, 1.3±1.6‰ (X ± SD), indicating that the six drugs were negative in micronucleus test, having no Structural chromosome damage or damage to the spindle apparatus.