The CCND1 gene encodes cyclin D1, which is a key regulatory protein in the transition from the G1 to S phase of the cell cycle. Amplification of CCND1 and over-expression of cyclin D1 were found in a variety of cancers, especially colorectal cancer. There are conflicting reports about the influence of the G870A polymorphism in the CCND1 gene on colorectal carcinogenesis . We evaluated the allelic frequencies and genotype distribution of this variant in a group of 167 colorectal cancer patients from the Republic of Macedonia, and compared it to those of the control subjects from the same population. Our data indicate that the CCND1 polymorphism may influence age at onset of colorectal cancer in young patients only when their tumors exhibit a microsatellite instability (MSI) phenotype.