Polymorphisms in genes involved in the complex mechanisms of carcinogenesis may affect the susceptibility to cancer. The multifunctional cytokine tumor necrosis factor alpha (TNF alpha) has an important role in the pathogenesis of inflammatory, autoimmune and malignant diseases. It has a large spectrum of activities, including both antitumorigenic and protumorigenic. In recent years, several TNF alpha promoter polymorphisms have been identified and related to the expression level of cytokine and to the susceptibility to solid tumors. The aim of our study was to investigate the frequency of three TNF alpha promoter polymorphisms (-1031, -308 and -238) in benign (fibrocystic changes) and malignant (invasive carcinoma) breast lesions. Using "real-time" PCR SNP analysis these polymorphisms were determined in 76 patients with benign and 158 patients with malignant breast lesions. The high expression genotypes at any of the three SNP polymorphisms were more frequent in invasive breast carcinoma (in 81 of 158 examined, 51.3%) than in fibrocystic changes (in 33 of 76 examined, 43.4%). The combined frequency of high production genotypes (-1031 T/C and C/C, -308 G/A and A/A and -238 G/A and A/A) was higher in patients with invasive breast carcinoma than in those with fibrocystic changes. However, these results were not statistically significant. Further studies on a larger group of patients are needed to evaluate the significance of potential differences in TNF alpha genotypes in different breast lesions.