Abstract: Objective To explore the levels of serum C reactive protein(CRP)and homocysteine(Hcy)in elderly patients with dementia and their correlations with severity of dementia. Methods The serum CRP and Hcy levels were compared among AD group ［45 patients with Alzheimer's disease(AD)］, VD group ［35 patients with vascular dementia(VD)］ and control group(31 healthy controls). According to the severity of dementia, the patients were divided into mild dementia group, moderate dementia group and severe dementia group.The levels of CRP and Hcy in different groups were compared. Results The levels of CRP and Hcy in the AD group and the VD group were significantly higher than those in the control group(P<0.01), and the levels of CRP and Hcy in the VD group were significantly higher than those in the AD group(P<0.01). Correlation analysis showed that there were no significant correlations between CRP level and score of Mini-mental State Examination(MMSE)Scale, age and severity of dementia in the AD group(P>0.05). There was a significant negative correlation between serum CRP level and MMSE score in the VD group(r=-0.399, P=0.018), a significant positive correlation between CRP level and age(r= 0.426, P=0.011), but no significant correlation between CRP level and severity of dementia(P>0.05). In the AD group, the Hcy level was negatively correlated with MMSE score and severity of dementia(r=-0.732, -0.721, P=0.001, 0.001), but had no significant correlation with age(r=-0.172, P=0.258). In the VD group, the Hcy level was negatively correlated with MMSE score and severity of dementia(r=-0.402, -0.452, P=0.017, 0.006), but had no significant correlation with age(r=0.131, P=0.454). The levels of CRP and Hcy in mild dementia group(n=20), moderate dementia group(n=49)and severe - dementia group(n=11)were significantly higher than those in the control group(P<0.01), and the levels of Hcy in moderate dementia group and severe dementia group were significantly higher than that in mild dementia group(P<0.01). Conclusion In elderly patients with dementia, the detections of serum CRP and Hcy levels are helpful for the differential diagnosis of AD and VD, and may be helpful in judging the progression and prognosis of patients with dementia.