Flow cytometric analysis performed on two different crosses of Dura x Pisifera oil palm gave an accurate estimation of nuclear DNA content. The genome size of Elaeis guineensis was found to be 2C=3.76±0.09 pg and therefore ca. 3.4x10(9)bp. Embryogenic calli and plants showed the same ploidy level, but the measured 2C DNA values differed significantly. No variation in the ploidy level between three different types of calli originating from foliar explants, namely nodular compact callus, fast-growing callus and friable callus was observed. Since fast-growing callus (FGC), already identified as a source of 'mantled' phenotype variants, did not show any difference in their ploidy level, these results are consistent with the hypothesis of an epigenetic origin for this type of somaclonal variant.