: This program will determine the level of P-selectin in control and ADP-stimulated platelets from normal volunteers and patients with carcinoma of the breast and bowel. This test will use a commercially available fluorescently labeled antibody, CD62. The program will also determine the level of glycoprotein (GP) IIb/IIIa in these samples. The total amount of GP IIb/IIIa will be quantified with a commercially available fluorescently labeled antibody, CD41. The amount of activated GP Iib/IIIa will be quantified with FITC-labeled fibrinogen. A single blood sample will be taken from the normal volunteers. Three blood samples will be taken from the patients with carcinoma: upon entry to the hospital, one day after surgery, and the of release from the hospital. Samples of tumor tissue removed by biopsy from the patients and, when possible margins surrounding the tumor, will be tested for total GP IIb/IIIa binding and FITC-labeled fibrinogen binding by flow cytometry. These investigators will use statistical tests to determine if the platelet samples from normal volunteers differ from the platelet samples from the patients with carcinoma. Similarly, it will be determined if there is any correlation between the presence of GP IIb/IIIa in the tumor and the response of blood platelets. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE