The oil palm (Elaeis guineensis Jacquin) is a cross-fertilizing perennial monocotyledon of the Palmales order that originated in central and western Africa. Its interest for mankind lies in the high oil content of the mesocarp and kernel of its fruit, both of which depend on shell thickness, which is governed by a major gene (Sh) and by genes with quantitative effects. Three varietal types are clearly defined. The dura type, of Sh+/Sh+ homozygous genotype, has fruits with a shell thickness of 2 to 8 mm depending on the progenies. The pisifera, of Sh-/Sh- homozygous genotype, is usually female-sterile and produces rare fruits without a shell. The tenera type, a dura x pisifera hybrid of Sh+/Sh- heterozygous genotype, has fruits with a shell thickness varying from 0.5 to 4 mm depending on the genotype. Lesser lignification of the mesocarp in tenera and pisifera fruits results in fibres that are not found in dura fruits. The existence of such fibres in the fruit is a phenotypic criterion used by breeders to distinguish between tenera and dura genotypes. Bulked segregant analysis (BSA) was applied to the search for AFLP markers of shell thickness in oil palm fruits. In three progenies, we defined and screened 9 groups of segregant individuals according to variety and shell thickness. A candidate AFLP marker of the Sh+ allele coding for the presence of a shell was evidenced. The usefulness of such a marker once converted into a PCR locus or allele specific marker are discussed.