Loss of BRCA1 heterozygosity represent a molecular alteration occurred in colorectal cancer, with unfavorable consequence on survival and that can be considered an independent prognosis factor in the steps I and II of colorectal cancer stage. The partial or total deletions generally involve a loss of heterozygosity which can have as a consequence the elimination or the inactivation of a tumoral suppressor gene. A series of frozen sections of colorectal cancers tumours were examined by FISH in order to investigate the alterations at the level of 17q chromosome where is located the BRCA1 gene. Sample imprints were obtained by applying the cut surface (5µ) on sialinized slides. Analyzed sections were from tumours divided in three regions (top, middle and bottom), and from control safe regions. Fluorescent images (digitally captured using a camera attached to a Zeiss Axioplan 2 imaging microscope, and tinted using MetaSystems ISIS software) were obtained for all tumours regions. Our results are preliminary. Only two patients of a ten individuals group were studied and we remarked some differences among analyzed regions. The next step of our experiment will be allelic imbalance examination of these regions in order to confirm/infirm eventually chromosome deletions in the 17q region.