The karyotype of the teleostean Gymnothorax tile was analysed by replication banding in order to clearly identify the homologous chromosomes. The RBG pattern was then compared to those of the other Muraenidae studied (G. unicolor and Muraena helena) and banding homologies of nine chromosome pairs were pointed out. A single nucleolar organizer region (NOR) was localized by FISH, silver- and CMA3-staining on the short arm of the pair 12. Telomeric (TTAGGG) repeats were terminally localized by FISH on all the chromosome pairs. The genome size and the AT-DNA content were evaluated by flow cytometry. Available cytogenetic data on the Muraenidae were then compared and discussed.