Ent-kaurene (ent-kaur-16-ene) and squalene were analyzed in extracts of the shoots of three cultivars of rice (Oryza sativa L.) of 14 and 28 days of age by gas chromatography-mass spectrometry (GS-MS) and GC-selected ion monitoring (GS-SIM).Ent-kaurene occurred at approximate concentrations of <1 to 13 ng/g f.w. in 14-day-old plants and 26 to 147 ng/g f.w. in 28-day-old plants. Shoots of the dwarf cultivar Waito-C contained much lessent-kaurene than the other two cultivars at both developmental stages. The level ofent-kaurene in the dwarf cultivar Tan-ginbozu was similar to that in the normal cultivar Nihonbare at 14 days but was lower than in Nihonbare at 28 days. Trace amounts ofent-isokaurene (ent-kaur-15-ene) were also found in the extracts of all three cultivars of shoots at 28 days. Squalene occurred in approximate concentrations from as low as 19 ng/g f.w. in 28-day-old Waito-C shoots to as much as 626 ng/g f.w. in 14-day-old Nihonbare shoots. Both Tan-ginbozu and Waito-C shoots contained less squalene than Nihonbare shoots at both developmental stages.