Seven new polyoxygenated cyclohexenes, named uvaribonol A-G (1-7) have been isolated from the ethanol extract of the stems of Uvaria boniana Finet. (Annonaceae), and their structures, including the absolute configuration, were determined by spectral and chemical methods. In vitro cytotoxicity test against several human tumor cell lines indicated that all of the new natural compounds are inactive, but some of the derivatives showed obvious activities. Compound 2a is the most active, exhibiting significant cytotoxicities against KB and Bel7402 cells with IC50 < 1 microgram.ml-1, and against HCT-8 cell with IC50 < 0.1 microgram.ml-1.