The role of DNA methylation in the regulation of gene expression and its implication in somaclonal variation has been extensively investigated. Significant changes in the methylation level of genomic DNA during dedifferentiation and somatic embryogenesis have been reported for higher plants. The occurrence of somaclonal variants (ca 5%) among populations of somatic embryo-derived oil palms (Elaeis guineensis Jacq.) currently hampers the scaling-up of clonal plant production. Variant "mantled" palms show a feminisation of flower male parts, which can result in complete sterility in the most severe cases. Given the observed features of the abnormality (spatial heterogeneity, temporal instability, non-Mendelian sexual transmission, absence of any detectable defect in DNA organisation as revealed by AFLP/RAPD studies) the hypothesis of an epigenetic alteration of genome expression has been proposed to explain the origin of the variant plants. The relationship between the "mantled" variation and hypomethylation of genomic DNA has been assessed, using two complementary approaches: HPLC quantification of relative amounts of 5-methyl-deoxycytidine and the Methylase Accepting Assay (MAA), based on the enzymatic saturation of CG sites with methyl groups (Jaligot et al., 2000). RFLP and AFLP studies are currently implemented, using isoschizomeric restriction enzyme pairs showing differential sensitivity to the methylation of dC residues (eg MspI and HpaII). As active chromatin may show reduced methylation rates as compared with its inactive counterpart, we are now comparing methylation rates in DNA corresponding to active chromatin in normal and variant regenerants.