Transgenic oil palm plantlets containing the transgenes, phaA, phaB and phaC responsible for the synthesis of polyhydroxybutyrate (PHB) were analysed using flow cytometry (FCM), cytological and fluorescence in situ hybridisation (FISH). Flow cytometry analysis was carried out to determine the nuclear DNA content of the transgenic oil palm. Analysis of the results showed significant differences between all the transgenic events and DxP regenerated plantlets (control). The mean genome size for DxP regenerants (2C = 3.52 ± 0.30 pg) was smaller compared with all the transgenic events, which had different genome sizes: TE 3-11 with size 2C = 4.38 ± 0.37 pg, TE 7-22 with 2C = 4.31 ± 0.26 pg, TE 4-5 with 2C = 4.09 ± 0.31 pg, TE 6-4 with 2C = 4.07 ± 0.63 pg, TE 9-4 with 2C = 4.01 ± 0.25 pg and TE 11-15 with 2C = 4.01 ± 0.37 pg. Cytological analysis showed no chromosomal aberrations such as anaphase bridges or lagging chromosomes. FISH analysis showed integration of transgenes on one or two chromosomes, targeting the distal region of long and middle length chromosomes.