Purpose and Background: Deterioration following improvement (DFI), refers to patients with cerebral infarction after thrombolytic therapy in improved condition, in a short period of time for various reasons re-aggravating the phenomenon of illness. DFI was defined as any 2-point deterioration on the NIH Stroke Scale after an initial 2-point improvement after treatment by the National Institute of Neurological Disorders and Stroke (NINDS). At present, the reasons that led to DFI, including target vessel re-occlusion, cerebral hemorrhage and ischemia - reperfusion injury. Arteriosclerosis, the time between onste to thrombolytic therapy, thrombolytic dose, blood hypercoagulability, hypertension and other risk factors for its . It has been reported about its incidence in the 15% to the result of target vessel re-occlusion often. About 75% of DFI occurred at 24h after thrombolysis, the main performance-based improvement of clinical symptoms has been re-aggravated, such as deepening of consciousness, paralysis of limbs, and speech or sensory disorders, which leads disability and mortality to a corresponding increase . DSA or TCD examination for detection shows that the original opened vessels has been re-occlusion, CT or MRI examination showed brain edema, infarct size increases, such as cerebral hemorrhage secondary. There is still a lack of effective methods of prevention and treatment of DFI reports, strict compliance with thrombolytic indications, control blood pressure, limit the amount of thrombolytic drugs, to improve the blood rheology, not using anticoagulant drugs within 24h as far as possible, anti-inflammatory, and to remove free radicals has the potential to reduce the incidence of DFI. It is currently lack of the clinical characteristics and treatment, prevention and prognosis of DFI. In this paper, 63 patients of cerebral infarction with arterial thrombolytic therapy within 4 years in our hospital of the retrospective study, clinical data collected in general, in accordance with the progress of the disease is divided into non-DFI and DFI Group; At the same time 117 cases of cerebral infarction patients who is similar to the DFI patients’Clinical characteristics did not receive thrombolytic therapy as the control group in order to preliminary explore the clinical features of DFI, the relationship between the test results and prognosis, and the effective prevention and treatment methods, in order to provide a reference for clinical treatment of observations. Data and Methods: In this paper, for the retrospective study, all data from the First Clinical Hospital of Jilin University Department of Neurology, November 11, 2004 to 2008 December 30 the line during the day, a total of 63 patients who received thrombolytic therapy in cerebral artery onset, including 39 cases of DFI group and 24 cases of non-DFI; 117 cases was selected who with similar clinical features to the DFI patients, did not receive thrombolytic therapy of cerebral infarction for the control group. The clinical data of patients were collected, including the gender, age, past history, clinical manifestations, examinations and treatments. Evaluation of the use of NIH Stroke Scale (NIHSS) of patients admitted to the stage score, according to the score fluctuations divided into DFI groups and non-DFI groups; At the same time by the score of patients admitted and discharged with the rate of change is divided into improved group and non-improvement group, compared groups of patients with NIHSS score recovery.Results: A total of 103 cases of thrombolytic therapy in patients with 63 cases’NIHSS score after more than two points lower, or 61.17 percent, but 39 cases have deterioration following improvement, as high as 37.86%. 12 cases aged over 70 years effective thrombolytic made 10 cases of patients DFI, accounting for 83.33%. DFI patients increased average temperature 0.6℃24h after surgery, there are 10 cases with temperature above 37.5℃. Three cases of combined application of balloon dilatation, angioplasty during thrombolytic therapy occurred DFI. 4 cases of posterior circulation infarct patients with arterial thrombolysis in the final 3 people were killed. 16 cases were confirmed by head CT cerebral hemorrhage after thrombolytic therapy, in which 1 case received surgery to remove hematoma, no patients died due to cerebral hemorrhage. DFI Group on 39 cases of the death of 7 patients, no significant improvement in 4, after 24h and 3 days after NIHSS score was significantly higher than non-DFI groups; 117 cases in the control group of 31 people were killed and 28 cases of no significant improvement, and in hospital 10 days NIHSS score was significantly higher than DFI group; no DFI group were significantly improved. DFI Group on 39 cases in 30 cases occur DFI within 24h, accounting for 76.92%, 10 cases of patients treated with the application of the expansion occurred in 6 cases of thrombolytic therapy after 24h, with a X2 test and the X2 value is 10.328, P = 0.001.Conclusion: The high blood pressure, diabetes, and smoking history, such as not to increase the incidence of DFI after thrombolysis, but the age of thrombolytic therapy over 70-year-old who carried out several significant increase in DFI. DFI occurred in more than thrombolytic therapy within 24h after onset, and more because of the re-occlusion of blood vessels. The expansion of blood volume therapy can delay DFI occurred, perhaps to reduce the incidence of DFI.. When the body temperature increased after thrombolytic therapy should be vigilant against possible occurrence of DFI. Patients with posterior circulation infarct after thrombolytic effect occurred DFI were significantly increased mortality. The head CT examination can be found abnormal changes, such as secondary brain hemorrhage, brain edema. The timely medical treatment for DFI reasons such as the control of cerebral edema, brain hematoma removal, may improve the prognosis of patients with DFI. Increase the incidence of DFI patients, the prognosis of patients with severely affected, but in the end the outcome of thrombolytic therapy still better than those who are not well implemented.