We reported recently on the isolation and structural elucidation of two novel antileukemic glycosides, bruceoside-A and -B, and brucein-D and -E from the H₂O extract of Brucea javanica ("Ya-Tan-Tzu"). Further investigation on the CHCl₃ extract of the same plant, which showed potent in vivo antileukemic activity against P-388 lymphocytic leukemia in mice, has now led to the isolation and characterization of brusatol and cleomiscosin-A. Brusatol was previously obtained as the aglycon from an acid hydrolysis of bruceoside-A and -B. Brusatol showed potent antileukemic activity in P-388 leukemia (T/C=158 at 0.125 mg/kg/d, ip). Cleomiscosin-A is active in the in vitro P-388 lymphocytic leukemia (ED₅₀=0.4 μg/ml) and is not active in the in vitro KB (ED₅₀>10 μg/ml) system. Cleomiscosin-A was previously isolated from Cleome viscosa, Simaba multiflora, and Soulamea soulameoides.