We hypothesize that interleukin 1alpha (IL-1alpha) and interleukin 1beta (IL-1beta) are present and tumor cell associated in human breast cancer (HBC) specimens. To test our hypothesis: a) immunologic analysis was performed on HBC histologic sections for IL-1alpha (n=49) and IL-1beta (n=42) distribution; and b) homogenates of HBC tumors were analyzed for levels of IL-1alpha (n=82), IL-1beta (n=101) and interleukin 8 (IL-8) (n=103) expression. Immunohistochemical analysis demonstrated the presence of IL-1alpha and IL-1beta in tumor cells in patients with invasive cancer and ductal carcinoma in situ. Quantitative analysis confirmed the presence and positive correlation of IL-1alpha and IL-1beta to IL-8, a known angiogenic factor, in cancer specimens. These studies demonstrate that tumor-associated IL-1alpha+, IL-1beta are present in the tumor microenvironment and may play a pivotal role in regulating breast tumor growth and metastasis.