The NOD2 gene has been associated with susceptibility to Crohn's disease, and more recently with carcinoma of the colon as well. NOD2 is involved in the inflammatory response and the activation of the NFkB pathway. The range of cancer types associated with NOD2 has not been well studied. The 3020insC allele results in a truncated NOD2 protein and is present in approximately 7% of the population. We studied a possible association between the 3020insC allele of the NOD2 gene and breast cancer using 462 cases and 1910 controls from Poland. Patients were diagnosed with invasive breast cancer at are of two Szczecin regional hospitals between 2002 and 2004. Pathology specimens were reviewed for histological subtype and for the presence of ductal carcinoma in situ (DCIS). Overall there was no association between breast cancer and NOD2 (OR = 1.1; p = 0.76), but significant associations were observed between the presence of the allele and early-onset breast cancer (OR = 1.9; p = 0.01) and between the allele and ductal breast cancer with an in situ component (OR = 2.2; p = 0.006).