Constitutive heterochromatin patterns of five domestic duck breeds three of Anas platyrhynchos (Dumyati, Khample and Pekin) and two of Cairina moschata (Muscovy and Sudani) occurring in Egypt have been described. Results indicated that although the constitutive heterochromatin (C-banding) pattern of three Anas platyrhynchos breeds shared the same distribution of heterochromatin there was an obvious variation in heterochromatin size. In addition, the C-banding patterns of the two Cairina moschata breeds (Muscovy and Sudani) were approximately similar. There wasvariation in size, number and occurrence of C-band blocks on micro-chromosomes between the examined five duck breeds. This may be attributed to the variation of euchromatin content and its correlation with chromosome size and arrangement of constitutive heterochromatin. Furthermore, it may be due to genome mixing through hybridization between related species and/or genera. The present results have shown that discrimination between Anas platyrhynchos (Dumyati, Khample and Pekin) and Cairina moschata (Muscovy and Sudani) duck breeds could be realized via cytogenetical markers such as presence of entirely heterochromatic chromosome pair no.8 in breeds belong Anas platyrhynchos whereas it was euchromatic in breeds of Cairina moschata. In addition to chromosome pair no.8, C-banding pattern of autosome pair no.3 and sex chromosome Z Could discriminate between the duck breeds of Anas platyrhynchos and Cairina moschata. Moreover, the constitutive heterochromatin amounts have significantly varied between the ducks belonging to the two genera. Thus, about only one-third of the micro-chromosomes in the three Anas breeds, exhibited large and visible C-banding blocks in both males and females while up to half of them in the two Cairina breeds. Hence, the duck breeds common in Egypt could be distinguished from others occurring elsewhere by C-banding pattern but this will be confirmed in further biochemical and molecular studies (under publication).