Constituents of supercritical CO2 extracts of peel and flesh from pummelo fruits (Citrus grandis Osbeck) were analyzed by gas chromatography-mass spectrometry (GC-MS). In total, 69 constituents were identified while 42 were common in both samples. The identified major constituents are 7-Methoxy-8-(2-oxo-3-methylbutyl) coumarin (11.4 %), (6E,8E,10E)-2,6,11,15-tetramethyl-2,6,8,10,14-hexadecapentaene (5.9 %) and gamma-sitosterol (5.1 %) in peel and hexadecanoic acid (10.0 %), (E,E)-2,4-decadienal (6.3 %) and pentacosane (7.0 %) in flesh extracts. Antiproliferative activity, determined by cell viability assay and cellular morphology observation, revealed that 400 mu g/ml concentration of peel extract possesses significant efficacy and potency for inhibition of human cervical carcinoma HeLa and gastric adenocarcinoma AGS cells.