Objective:To investigate the early MRI appearances and pathologic basis of cryptococcal neoformans infection in rats. Methods:96 Wistar rats were randomly divided into(1)immunocompromised infected group(n=40),(2)normal status infected group(n=40),(3)simple immunosuppression control group(n=8),(4)normal control group(n=8). Infected rats were injected intracerebrally with the suspension of cryptococcus neoformans. At 7,14,21,28 days,the rats were scanned with conventional imaging,enhancement scanning,and DWI,and then were killed to observe the pathological changes of lesions. Results:(1)Meningeal enhancement:At 7 days,MRI showed meningeal enhancement in infected rats. Meningeal enhancement observed in rats of immunocompromised infected group and normal status infected group were 4,4,3,3 and 2,1,1,1 respectively at 14,21,28 days.(2)Brain parenchymal lesions:1,3,6,6 and 0,0,1,1 lesions of the two groups were seen respectively at 7,14,21,28 days. There were significant differences(P=0.04)between the two groups at 21,28 days respectively.(3)Dilated ventricle was observed in 4 immunosuppressive rats and one normal status infected rat at 21 days. More obviously dilated ventricle was seen at 28 days of the two groups,respectively for 6,1 rats.(4)Brain lesions became larger and more with time,in dynamic observed group in rats of immunosuppressive status.(5)Pathological examination:Cryptococcus neoformans were seen on part of meningitis and in the brain parenchyma. The gelatinous pseudocysts around the cryptococcus neoformans,lymphocytic infiltration,focal necrosis were observed with HE and PAS staining. Conclusion:Immunocompromised rats are easier to be infected by cryptococcal neoformans. The earliest finding of cryptococcal neoformans infection in rats on MRI was meningoencephalitis. MRI findings of brain parenchymal infection shows limited inflammation,gelatinous pseudocysts,and dilated ventricle.