Objective To investigate the spontaneous neoplastic lesions and their incidences in rats .Methods Sixty male and 60 female specific pathogen-free Wistar rats (4-weeks old ) were used in this study .The rats were acclima-ted for 1 week prior to initiation of the experiment .They were fed with conventional feed for 104 weeks and then sacrificed for histopathological examination .Results Various neoplastic lesions of the rats and their incidences were analyzed and reported.For male rats, their total tumor incidence was 49.12%, the benign tumor incidence was 38.60%and the malig-nant tumor incidence was 17.54%.The benign neoplastic lesions mainly were pituitary adenoma ( 19.30%) , testis Leydig cell tumor (5.26%) and subcutaneous fibroma (5.26%).The malignant neoplastic lesions mainly were squamous cell carcinoma (7.02%) and lymphoid hematopoietic system tumors (3.51%).For female rats, their total tumor inci-dence was 60.34%, the benign tumor incidence was 50.00%and the malignant tumor incidence was 15.52%.The benign neoplastic lesions mainly were breast fibroadenoma (25.86%) and pituitary adenoma (24.14%).The malignant neoplas-tic lesions mainly were adenocarcinoma (5.17%) and breast cancer (3.45%).Conclusions The spontaneous neoplastic lesions and their incidences reported in this paper provide another data of the spontaneous tumors of SPF Wistar rats and may provide some reference for relevant technical staffs .