OBJECTIVE: Risk factors leading to development and subsequent progression of chronic venous insufficiency after acute deep venous thrombosis (DVT) are only partially identified. Inflammation and rheologic abnormalities might have a causative role. The purpose of this study was to investigate C-reactive protein (CRP), D -dimer, and blood rheologic parameters in patients after acute DVT in relation to clinical outcome. SUBJECTS AND METHODS: Patients with a history of acute proved DVT underwent clinical examination and duplex ultrasound scanning of the veins, and Venous Clinical Severity Score (VCSS) and Venous Segmental Disease Score (VSDS) were calculated. Further, CRP, D -dimer, and several rheologic parameters were determined and related to outcome as assessed with venous scores. RESULTS: Forty-three patients were examined 28 (median) months after the index event. Patients had higher CRP ( P < .001), D -dimer ( P < .001), red blood cell aggregation ( P < .01), fibrinogen concentration ( P < .01), and leukocyte count ( P < .05) than did healthy control subjects. CRP and red blood cell aggregation were positively correlated with VCSS ( r = 0.42 and P < .01, and r = 0.30 and P < 0.05, respectively). Multivariate regression analysis showed that the relation between CRP and VCSS was independent of other laboratory and rheologic parameters and of age, total thrombus load, duration of compression therapy after the index event, recurrence, recanalization, and presence of comorbid conditions ( P < .05). CONCLUSIONS: CRP is independently related to the severity of venous dysfunction in patients after acute DVT. Chronic inflammation as well as changes in blood rheologic parameters may be causally involved in the development of chronic venous insufficiency occurring in the medium-term and long-term course after acute DVT.