The essential oil of Tanacetum gracile (Accession no. AT-01 termed AT-01 in the manuscript), a cold desert alpine highly aromatic herb, has 40 constituents including lavendulol (21.5 %), lavendulol acetate (1.7 %), alpha-pinene (11.2 %), 1,8-cineole (15.2 %), CIS-beta-ocimene (6.9 %), borneol (6.1 %), limonene (5.1 %) and chamazulene (3.7 %). AT-01 was evaluated for its anticancer activity. It inhibited HL-60 cell proliferation with an IC (50) of 27 microg/mL. Furthermore, AT-01 induced apoptosis in human leukemia HL-60 cells as measured by several biological end points. AT-01 induced apoptotic body formation, enhanced annexinV-FITC binding of the cells, increased sub-G (0) DNA fraction, loss of mitochondrial membrane potential (Deltapsi (mt)) and release of cytochrome c from mitochondria, activated caspase-9 as well as caspase-3, and increased cleavage of PARP in HL-60 cells. Thus, AT-01 induced apoptosis through the mitochondrial dependent pathway in HL-60 cells.