Objective To study the character of multiple primary malignant neoplasms (MPMN) in patients with bladder cancer.Methods From 1958 to 1998,patients with bladder cancer associated MPMN were studied retrospectively.Results MPMN was found in 49(5.7%,49/847) patients with bladder cancer,including 32 male and 17 female.All the bladder cancer were urothelial carcinoma,47 cases of non muscleinvasive urothelial carcinoma and 2 muscle-invasive.47 cases were double-primary cancer patients,and 2 triple-primary.Non-bladder primary malignancies were found in digestive system(36.7%),respiratory system (20.4%),genital system(20.4%),and other system(20.4%).Lung cancer was the second primary cancer in 7 cases(14.3%,7/49).The MPMN were diagnosed at the same time in 5 cases,and the others one after another.Bladder cancer was the first primary cancer in 25 cases,and 24 as the second primary.The mean age when the first cancer was diagnosed was 51y.It was 86.2 months between the first cancer and the second for the mean time.90% cancer was in clinical stage Ⅰor stage Ⅱ.The median survival time was 39 months after the second primary malignant,and 104 months after the first primary malignant.Conclusion The most pathology type of the bladder cancer in MPMN is non muscle-invasive urothelial carcinoma. Non-bladder primary malignancies are found more common in digestive system,the following are respiratory system and genital system.When lung cancer is the second primary malignant,it should be discriminated from metastasis of bladder cancer.90% cancer is in early clinical stage.They will have a good prognosis if diagnosed early and treated properly.