Physical mapping of rRNA genes by in situ hybridization was performed on Elaeis species chromosomes. Fluorescence in situ hybridization (FISH) was perforrned on Elaeis oleiferachromosomes with probe pBG35 which contains 18S-25S rRNA genes from flax. Hybridization sites were located on the telomeric regions of an acrocentric pair of chromosomes and their satellite DNAs. Multiple labelling FISH was used to physically map the 5S and 18S-5.8S-25S rRNA multigene family in the interspecific hybrid of E.oleifera x Elaeis guineensis (OxG). Two heterologous labelled probes with 18S-25S (pTa 71) and 5S (pTa 794) rDNA were used for in situ hybridization of these chromosomes. It was found that 5S genes are situated on the proximal arms of the longest chromosome pair, or pair No. 1. The 18S-5.8S-25S rRNA genes are located on the telomeric regions of an acrocentric pair of chromosomes and on the satellite DNAs. The technique can now be used to locate other sequences of interest in the Elaeis species