Objective To explore the spontaneous non-tumor lesion of kidney and its correlation with different age and sex in SD rats. Methods Eight hundred specific pathogen free SD rats were collected from the blank control groups used in subacute toxicity tests,subchronic toxicity tests and 1 or 2 years of chronic toxicity combined with carcinogenic tests. Rats were randomly divided into 4 groups with 10,19,56 or 108 weeks of experimental periods. Each group consisted of 100 female and 100 male rats. The renal tissu...