C-band heteromorphism, including size and localization variants, has been shown to correlate well with the occurrence of malignant diseases. The study was conducted with the aim of investigating aberrations of the C-band region of chromosomes 1, 9 and 16 including size variation, intra pair size asymmetry and inversion by comparing the frequency of heteromorphism in patients with breast cancer and healthy subjects. This is useful to establish the significance of variability of chromosome constitutive heterochromatin areas in a risk of malignancy. The study included 27 female patients with breast cancer and 30 normal healthy female subjects as controls. Peripheral lymphocytes culture and C-banding were done for all of them. The size of the heterochromatic region was evaluated using 16 p as a reference. Size heteromorphism between homologous chromosomes was considered when there was an intra-pair difference of one or more levels. Inversions whether partial or total were recorded. There was a significant increase in size of C-band for chromosome 1 between patients and controls [X2 = 9.17]. Intra pair size asymmetry of heterochromatin was more frequent in breast cancer patients than in the controls and the differences were statistically significant for chromosomes 1, 9 and 16 [X² = 4.4, 5 and 4 respectively]. For localization variants, a significant increase in frequency of partial inversion in chromosome No. 1 was found between the two groups [X2 = 4.44]. In conclusion, the present study showed that C-band heteromorphism occurs with higher frequency among breast cancer patients and supports the reported bassociation between presence of C-band heteromorphism and occurrence of malignant disease.