The present study was carried out on Nile perch, Lates niloticus to determine its standard karyotype as well as the number and localization of nucleolus organizer regions (NORs) in its chromosomes. The distribution of heterochromatin in Lates niloticus chromosomes was also investigated. Specimens used in this study were treated with the suitable methods for normal chromosomal analysis and banding studies in fish. The obtained results showed that the normal diploid chromosome number in mitotic cells of this species is 2n = 48. This diploid chromosome number was confirmed by studying meiotic chromosomes prepared from gonad cells of both males and females. The formula proposed for Lates niloticus is n = 1M + 1SM + 1 ST + 21 A with FN = 52. Comparison of karyotypes from male and female somatic cells did not reveal any specific heteromorphic sex chromosomes. 
C-banding studies showed slightly stained centromeric heterochromatin in seven pairs of acrocentric chromosomes. One of these chromosomes also showed heterochromatin in telomeric region.
NOR-banding analysis revealed one Ag-NOR band located in telomeric region of the long arm of one large-sized telocentric chromosome pair. No differences were detected between males and females in the distribution of the C-heterochromatin and NORs banding pattern.