BACKGROUND: Platelets are an important element in the thrombotic process, inflammation and cancer progression. We tested the hypothesis that there is a relationship between platelet activation and inflammation in colorectal cancer patients (CRC). PATIENTS/METHODS: We measured soluble (s) P-selectin (marker of platelet activation), interleukin-6 (IL-6) and C-reactive protein (CRP) (indexes of inflammation) in 42 CRC patients and 38 healthy subjects. CRC patients were divided into two groups: A-24 patients in stages I and II; B-18 patients in stage III. Soluble P-selectin, Interleukin-6 concentration was measured using commercially available immunoenzymatic methods. High sensitivity C-reactive protein (RCRP) concentration was measured by a high sensitivity latex particle turbidimetric immunoassay. RESULTS: Soluble P-selectin, CRP and IL-6 levels were significantly increased as compared to the control group (p<0.001). Plasma levels of sP-selectin, CRP and IL-6 were higher in group B (with metastases) than in group A (without metastases) (p<0.001). CRC patients had a positive correlation between IL-6 and CRP (r=0.7638, p<0.01) and between sP-selectin and IL-6 (r=0.5633, p<0.03). CONCLUSION: We observed hyperactivation of blood platelets and inflammatory response in patients with colorectal cancer, also the inflammatory process and platelet activation progress along with colorectal cancer advancement. Our results seem to confirm the relationship of platelet activation with inflammatory response in colorectal cancer patients.